I consider Omnitron slightly easier than Baron Blade, although the swing is most obvious in a 5-player game on Advanced mode…3-player or non-Advanced games are about even I think. But aside from the several mistakes you've made, some of which have already been pointed out, the bottom line is that Omnitron is very slow, and most of his threats can be counteracteed quickly. Sedative Flechettes is a wrecking-ball of a card, but he only has two; Technological Singularity and Terraforming are both potentially blank, his Repair Drones only delay the inevitable, all his Drones are easy to kill, his Components (except Interpolation Beam) don't fire until the start of the next turn and are quite easy to destroy before then with any sort of decent damage-dealing party…the only really strong cards in his deck are Flechettes, Electro-Pulse Explosive, and the Adaptive Plating if you don't have a diverse party. Also the Environment makes a difference; because Omnitron is invariably higher-HP than heroes while his Drones are extremely low, it's common for environment cards that target high or low HP to work in your favor. (Ones that target second-highest or -lowest HP are more of a problem, of course.)
Above all other heroes, the ultimate wrecking ball to Omnitron is The Visionary. Precognition and Suggestion on his Factory turns will entirely neuter him by forcing him to play a blank card, and even when he's a Rampaging Robot, he's much less dangerous playing 1 relevant card than 2. Visi can also use Wrest the Mind to entirely neutralize Electro-Pulse Explosives (when it tries to deal 15 damage to the first of all hero targets, you redirect that damage to itself, it's destroyed, and Visi doesn't even take 3 damage herself because Wrest the Mind was destroyed along with its target); failing that, she can have a weak Drone hit Omnitron and then kill itself instead of hitting a hero.
I'm not sure which errata that would be; I'm a newcomer to the game so I've never seen the pre-Enhanced Edition version.
He kept pulling sedative flechettes over and over again, which I found to be really annoying. And what's really ironic is I found what I wasn't even playing the game right. When his brought a drone out at the end of his turn I didn't bother using its end-of-turn effect since it just came out right at the end of the villain turn.
Since we've established that you weren't supposed to get that many Flechettes, I'd say two wrongs were making a right here. I once had a game in which I beat Omnitron by accidentally allowing one of his Drones to attack all targets instead of just one…he killed Tachyon, who was right before Unity in the turn order, and Unity's deck is made mostly of extremely powerful robots that are impossible to play on your own turn without jumping through some hoops. But Tachyon can grant a card play while Incapacitated, and since it's not Unity's turn, she can just plunk down a robot without any difficulty. Thusly, Tachyon was far more useful dead than alive, and Visionary was also in that game (and we were in Insula Primalis, where the Velociraptors invariably attacked Drones, and the T-Rexes were Wrested by Visionary into attacking Omnitron after having legally done so once, because he had lower HP than the second Tyrannosaur) - nevermind, I'm mixing up a different pair of Visionary games, one with Omnitron and one on Insula, but the time they were both there this did not happen. (I have had her throw a Monorail car at Omnitron with Wrest the Mind when they were in Metropolis, and I've had her Wrest a Tyrannosaurus once, but that was against Ambuscade.)
he got out adapative armor plating, then tempest was incapacitated and the other two heroes were unable to do anything to him since they both only deal projectible damage.
Bunker does have a few cards that deal other damage types - External Combustion for fire and Omni-Cannon for Energy I believe. Wraith occasionally does melee (although it is weird, given that her shtick is being Batman, that she hasn't prepared any Equipment that can deal with this problem). And occasionally the dinosaurs will deal melee damage to him and give you a window to get through the Plating that way, plus the Plating can simply be destroyed with a Grappling Hook or Ball Lightning or something. But yeah, if Plating comes down against the wrong group of heroes, it's sort of a "You Lose" card unless you luck into the right way around it. Omnitron has a lot of cards like that, which is part of why Visionary, the ultimate deck-manipulation hero, is such a magic bullet against him.
This time, I chose to flip omnitron on the first turn (since the card does say to do that, and it gives no indication you're not supposed to on the first turn, and besides that I thought it might make it easier on me).
He does indeed flip on the first turn - he technically starts the game as a Factory, but the first thing to happen in every game is that he goes Rampaging and plays two Villain cards. It'd be pretty silly for him to be a Factory on turn 1 since he'd have no trash to reshuffle in search of a Drone or Component; even as-is, his second-turn first Factory effect is almost always a blank, because if he plays a Drone on turn 1, you probably won't bother to kill it, knowing he'll get it right back. And if he plays a Component, and you're able to destroy that Component before his next turn so he gets it back…well, then you can probably destroy it again just as easily. Usually it'll be at least turn 4 of the game before he'll raise anything from his trash.
Right after Zero got his two main equipment out, he pulled a technological singularity
Right, that's a clear example that these games were not destined to go your way. Sometimes you get the bear and sometimes the bear gets you. Absolute Zero is one of the worst possible heroes to use against Omnitron for this exact reason - Bunker and Wraith suffer a fair bit if he does TechSing, but Zero in particular needs his Modules to do anything effective. He has issues against any hero who can destroy Equipment, such as Citizen Dawn or La Capitan, but Omnitron is the only one who adds insult to injury by punishing you for having ever played equipment. (Yet another reason why Visionary pwns him, as she doesn't have any. Traveled back in time with nothing but the clothes on her back, and saw no reason to change that after arriving.)
Omnitron btw managed to take my heroes down to about half within 3 or 4 turns.
That's not too unusual for any villain. The heroes nearly always take somewhat of a beating, but as long as they have 1 HP left, they're still in the game, and even an Incapacitated hero or two continues contributing with their flipside abilities. It's very common to have all the heroes down to 5 or 10 on the last turn of the game; it still doesn't mean that was even a particularly difficult fight. The game's balance point assumes that the heroes will knock down the villain's 50-100 HP (there are four exceptions to this range) at about the same speed that they deplete their own 25-30 HP (three exceptions there, more if you count promo heroes), due to the Villain's attacks as well as their own self-damage effects, with the Environment periodically messing with both sides.
I can't fathom why he's given the same difficulty rating as baron blade in the enhanced rule book (warlord voss is easy compared to omnitron).
Here you're just plain incorrect. You were playing Omnitron all wrong as has been established; played properly, he might be slightly harder than Blade, based on what others on this forum have told me, but my personal experience is that he's easier (the only time he's beaten me, it was largely due to a particularly nasty Environment, coupled with my getting lazy and overconfident). And Warlord Voss is probably the toughest of the original four villains, although an argument for Citizen Dawn could be made instead; I'm a bit biased because I just enjoy her more, but I still think Voss is tougher just by virtue of his brutal efficiency, coupled with the virtually unstoppable threat of Forced Deployment, the ability for Gene-Bound Guards to protect the rest of his army (who are admittedly quite squishy otherwise), and the fact that unlike with Dawn, it's completely impossible to ignore the army and just focus fire on him in order to end the game quickly. (If Dawn flips, you have to deal with the Citizens, but otherwise you can take out the most dangerous few of her initial Citizens, and then leave a relatively harmless one like Spring or Autumn in play, just to keep Dawn from flipping, and then just beat on her nonstop and hope the worst of the Citizens don't show up.)
All his cards are insanely powerful, I mean seriously h+1 damage to all heroes AND destroys all their ongoing cards, seriously?
That is definitely one of the most absurd cards in the game, no argument there. But look at how wimpy Automaton Drone is in a 3-player game (compare to the Blade Battalion, which are identical to a H=5 version of the Automatons, regardless of the actual H value). Assault Drones are always a squishy 4 HP and deal just 2 damage to one hero, unless other Drones are out, which will seldom be true because you can keep killing them off (if it were up to me, Omnitron would reanimate ALL his killed Drones every couple of turns, just to get the "robot revolution" flavor to really come through and make it a more sporting battle). Interpolation Beam is forgettable for most heroes unless you play on Advanced, and half the time even then; the other Components all wait until the start of Omnitron's turn to fire, and are usually easy to blow up before then by dealing 7 damage. Omnitron is very swingy in terms of his card power, which is one of the reasons he favors a longer game. If you get lucky on his first few plays, and consistently beat on him hard with a competent damage-dealing party, it's very possible to deprive him of even that massive 100 health before he can stabilize.
oh and let's not forget the electro-pulse explosive, which at least will deal 10 damage to everyone on the next villain turn.
Not true at all. Even ignoring the Visionary trick I mentioned above, let's look at a party of Haka, Legacy and Absolute Zero (I could go with Ra or Wraith or Bunker instead of Zero, but that would definitely make this a party of above-average deadliness). The EPE comes out on Omnitron's first turn (along with a Repair Drone or Terraforming or something similarly irrelevant), and then Haka gets a turn; Haka might Elbow Smash the EPE down to 12 and then Crush it to 10, or just put down his Taiaha and bonk the EPE for 3, let's assume the latter so it's left at 12. Legacy can THOKK! it down to 9, then Galvanize all the heroes. Absolute Zero plays Isothermic Transducer, then Thermodynamics himself for fire damage; because of Galvanize, the 1 damage is boosted to 2, and then Transduced into 2 damage which is boosted to 3, so he hits the EPE and knocks it down to 6. That was only a fairly average round, maybe slightly above what a completely random group of heroes with a completely random set of cards might be able to put together, but certainly far short of the deadliest example I could have constructed. (With five heroes including Legacy, Fanatic and Ra, it'd be far from unusual for the EPE to die halfway through the round and then for Omnitron to lose 10 or so HP thereafter.)
And I don't appreciate it when the one drone comes out and heals what little damage I did to omnitron (most of my attacks are spent taking out the drones)
Repair drones are good. You want to see repair drones, because they do absolutely nothing to set back the hero team. They just uptick Omnitron's HP a little; if that's all that ever happened, it would only be prolonging the inevitable. Aside from Terraforming with no Environments or TechSing with no Equipment, Repair Drone is the most innocuous card in Omnitron's deck, even more harmless than the Components which are only a potential threat. If you have to spend all your attacks taking out 3-5 HP drones, then your party is well below the median in effectiveness. If you're stuck playing a group like Chrono-Ranger, Legacy and the Argent Adept (in that order), then yeah, Omnitron is going to be a tough hill to climb. But even then, the Repair Drones are more of an insult than a threat. You'll be happy to see them instead of even a mildly dangerous card like the Assault Drone or Interpolation Beam, to say nothing of the actual threats like EPE, Flechettes, or a mid-game Terraforming.
How do you beat this guy? I see no way to do it, his deck has at least one card that completely counters every hero there is!
And what happens when he draws TechSing on turn 1, when even the most equipment-dependent hero hasn't played a card yet? What happens when he gets Adaptive Plating against a party of Ra, Fanatic, Zero, Haka, and Bunker, where no two of them share a damage type and most of them can do more than one? Omnitron has very few H variables on relevant cards (Automaton Drone isn't really that dangerous, as it hits only one hero and isn't hard to kill within one round, and the Disintegrator Ray will almost never fire in a high-H game; Flechettes is the only one where it really hurts), so the more heroes you have against him, the easier he is to beat, almost without exception. You've only done 3-hero games, so the deck was stacked against you, but even so, a careful selection of effective and diverse Heroes (and not making a HUGE rules mistake in his favor) would have easily rendered Omnitron a barely-credible threat. That, of course, is not really ideal…you want the game to provide some challenge, or what's the fun in bothering to flip all those cards? So I'd say next time you fight him, grab four random heroes and arrange them in an order that looks optimal, pick a more dangerous Environment like the Ruins of Atlantis (note: Pillars of Hercules or Font of Power into Electro-Pulse Explosives = VERY BAD, but the odds are pretty slim of that happening), and you'll find that he should provide you a good workout without making you feel totally screwed. If you still manage to lose that game due to bad luck, you then take a party of five including Legacy and Visionary (and excluding AZ), fight in the Wagner Mars Base or on Insula again, and prove to yourself once and for all that he can be beaten, often with embarassing ease.