I think those are a good place to start, but I'd like to see them have more internal cooperation (like the Prime Wardens or, hopefully, the Freedom Five.)
I think you could build an intriguing set of powers along the theme of "sharing the burden" or "Paying costs for your team" since it seems like the beginning of the team was all about sacrificing for one another (Expatriette pulling back, Setback growing more cautious, the team searching for a way to bring Mr. Fixer back.)
Take Mr. Fixer's power: as written it encourages building up a large hand, but that has the unfortunate side effect of discouraging him from changing stances (since they're destroyed instead of returning to his hand.) What if the power was:
Balanced Strike: As a team, players may discard a total of three cards. Deal One target X Melee Damage where X is the number of cards discarded this way.
or, if we think that's unclear and don't think the potential of Mr. Fixer hitting for five is too OP:
Balanced Stike: Each player may discard a card. Deal one targer X Melee Damage where X is the number of cards discarded this way.
A Fixer power that I thought of yesterday, but don't know where his health would have to be to make it acceptable:
Teaching Strike: Select a target. Until the start of your next turn treat all cards in Mr. Fixer's play area as though they were also in that target's play area, replacing all instaces of Mr. Fixer with the name of that target.
(This removes most of his ability to deal damage, but has some truly frightening implications. I mean can you imagine if he taught Char how to use a Jack Handle?)
(It should probably be hero target instead of target [if it should exist at all] but I very much wanted to conjur the image of a Jack Handle wielding Char. Thank you for indulging me.)
Nightmist's power isn't bad, but all other powers which have a random card play either have a way to mitigate it (Cosmic, Omnitron) or do an additional effect (PW Adept, PW Fanatic, Rogue KNYFE.) Given that you're going for "Wild Magic" maybe an additional effect is the way to go so perhaps:
Wild Magic: Put the bottom card of your deck into play. One player may put an equipment card from their discard pile into play.
(Or instead of discard pile, play from hand.)
If playing as a full Dark Watch team that helps Her, Fixer, and Expatriette, not to mention plenty of other heroes. If that seems too powerful it could always go to the top of their deck instead of into play.
Or, a power I thought of for a "help pay a cost" theme:
Life Bond (or something else, I'm not good with titles): The next time Nightmist would deal damage to herself another hero may redirect that damage to themself.
And finally, another power thought to take the mitigation aspects of Attunement, but to a slightly greater degree.
Concentration (I said I wasn't good at titles, and I meant it): Choose a number between 1 and 4. The next card Nightmist reveals has that [magic number] instead of it's normal [magic number.]
I like your idea for Setback's power, althought I do wish we could think of a good token generation power instead of token spend power. Karma does help a lot if you want Setback to use his "remove 2 unlucky tokens to redirect damage to Setback," which I want to use more than I do currently.
A similar power with a focus on Setback's attitude could be:
Chipper Attitude: Remove one [or two] Unlucky tokens from Setback's Unlucky pool. If you do, each hero regains One health.
(I just love his grin, it makes me happy.)
Expatriette may have the same bottom card issue as Nightmist (in that it may not do enough for the cost.) I don't know if this too powerful (or wordy, I do like my lengthy blocks of text,) but what it was:
Weaponsmith: Reveal the bottom card of your deck, if it is a gun card put it into play. If it is an ammo card deal one target one projectile damage activating the ammo's text as though it were next to a gun making that attack. Discard the ammo card. Otherwise, put the card in your hand.
or, less wordy (and consequently, less fun):
Weaponsmith: Reveal the bottom card of your deck, if it is an equipment card put it into play, otherwise discard it and deal one target two projectile damage [or: put it into your hand.]
Finally, I think we can all agree on this Harpy promo:
The Harpy: Fowl Friend
Hp: 28
Old Tricks: Take Matriarch's deck out of the box. Search the deck for all Fowl cards and put them into play into The Harpy's play area. Treat all instances of "Hero Target" as "Villain or Environment Target." Until your next play phase treat all start of turn effects on Fowl Cards as happening at the end of your turn as well. Return Matriarch's deck to the box. If a fowl card would be destroyed it is instead returned to Matriarch's deck.
It's only fair after the pain she's caused all of us over the years.