Question about Tachyon

So, Tachyon's Hypersonic Assault power lets her "attack multiple targets using Finesse". How many targets can it affect? I can't see a clear explanation.

The Green Zone explanation says she hits every target she can get to on foot.  So there is functionality no limit I can tell. 

Refering to "Whatever you can reach on foot" for a speedster character is asking for trouble when it comes to rules and such...

Well that’s what is listed in the character booklet.   Much like the card game version of the same card it hits every non-hero target it can.  

i personally rule it as all enemies in her starting location and another, and she has to end her attack in the other if she moves.

This ability seems very overpowered to me if it is unlimited. This means that in two rounds she can take out an entire horde of d6 minions single handedly because even if she rolls poorly and every minions saves, they will be reduced to d4s and then next time will be destroyed. I like the idea of zones, but there is no mention of this in the rules. Do I, as GM, set each group of three minions as being in a single zone? The problem I have with this is that I feel in story terms, Tachyon should be able to attack the entire horde of minions in one round regardless of how seperated they are, but maybe that if she does the attack shouldn't be enough to destroy them so quickly. To contrast this to the card game, the card hypersonic assault does 1 damage to each non-hero (villian?) target which is something, but not much at all.

I am currious how other people feel about this. Is this not a problem because minions are meant to be this weak? Or am I missing a more simple way to nerf this ability?

I kind of went with everything that hadn't made an effort to be difficult to get to, for example (Spoilers) In issue 1 when dealing with the spider hordes at the tree she could hit everyone, except for the snipers who fortified positions on teh walls and were trying to be difficult.That way any minion who isn't listed as defending or deliberatly being difficult should be fair game. I figure that's a fair way to work thorough it without being too stingy. Speedsters are notorious Mary Sue's. as anyone who's read the flash for very long can attest to. Christopher & Adam even talk about it in her Letters page. On the other hand minions are supposed to be weak and this is one of the few super hero games that isn't a single player video game that brings that accross well

I ran 801 and 802 for my gaming group on Tuesday, and yeah, Tach sweeps minions off the board like they were paper. And if Legacy Galvanizes Tach, the minions might as well not show up. Galvanized Tach was regularly throwing 6 and up against d6 minions. I think that's part of the reason why they blew through the issues so fast. 

Keep in mind that at least for Megalopolis, the team might not all be in the same area of the city. That’s part of what kept Tachyon (who I played during a demo at Gen Con) under control so everyone got a chance to beat up minions.