He does have a variant though it is based off the Dark Watch team.
I agree with Blackfang, it's such a shame they never made a variant for Setback. We all agree there's no variant, right? Just the normal awesome Setback. That's what he deserves.
great googly moogly
It's a shame he was left in the DARK, WATCH out, maybe one day we will get one!
Thoughts on a few of them;
Termi-Nation bunker I find works best with Turret Mode, or rather, coming out of Turret Mode. Use the first power usage for bosted damage, then destroy Turret Mode and switch in something new. Bunker kind of has an 'ideal' in his other variants, but TN is all about swapping and I think it's cool getting what amounts to a whole second turn all at once.
I love XPW Argent Adept. One of the best things about the base version is him letting other heroes play or use powers out of turn, and he can do that first turn, no matter what. He is awesome at the front of the queue -- put him with TN AZ and get a boosted Cold Snap out first turn with no risk. Let Scholar play a form and heal himself back up to do damage in a heartbeat -- or Know When To Hold Fast and still get a power usage this turn. It makes AA a little less reliable where his songs are concerned, but his base power does two of the best functions his songs have, in an order that's normally harder to do.
Now, PW Captain Cosmic I rarely use. Most of his deck is constructs, so if they're getting wiped out often enough for his power to be used, chances are you're facing mass damage so any construct you play now is just going down, too. I'd rather pump out more with his regular power most of the time.
Edited to add: XPW Captain Cosmic is awesome with some power boosts. Just did a game where he all but soloed Gloomweaver thanks to Legacy. If you can keep his constructs out, it's a power that only gets stronger as the game goes on and is amazing for focusing down a target.
I don't think I've used base Expat except by accident or in a Weekly One-Shot since unlocking her DWD variant.
I too enjoy PW Fanatic, though I'm usually careful to put her out front so that an ill-timed End of Days doesn't wreck everything.
I love PW Tempest. He actually gives me a reason to use his Elemental Subwave Inducer, and my biggest problem is always running out of cards.
PW Haka is fun -- especially if your opening hand is Savage Mana and Rampage -- but I tend toward his base version for consistency.
I, too, avoid DW Setback like the plague (rat). DW Fixer, though, I like using, even if there are turns I have to hold back. He's great with some heroes, though -- Setback seems to accumulate Ongoings that aren't needed, and he's great to pair with PW Fanatic.
Yeah, Hunted Naturalist is too good. Especially if you can get a form out and keep it out.
I really like how Scholar of the Infinite changes his priorities. I always try to play him as a tank.
DW Nightmist... yeah, that's another tough one. I like her better when she has some outside card draw and/or can get out-of-turn power uses (I, too, constantly forget what's on top). I almost always default to regular Nightmist, though.
I don't think I've used base Tachyon on purpose since TLT came out. I mainly use SST when I'm playing a 'gimmicky' game (i.e., have Sentinels play all the things).
That's more or less off the top of my head. Unfortunately I don't get to play the physical game often, so some of the newer variants I haven't gotten to test out. I, too, don't really get F5 Wraith, but I have seen F5 Tachyon clean house.
How's that breeze feel, Powerhound 2K?
is your head nice and cool?
I'm sorry that sarcasm doesn't translate well in pure text.
I did try to help you out a bit (since I picked up on what Blackfang was going for)...
Hence my further reply. No need to pile on.
No need to pile anything on, wouldnt do any good anyway. It'll just land right behind him as it passes over his head 
For Setback, I'd kind of like to see another 'the same but more' variant, like TN is to AZ. Maybe something that gives you 2 unlucky tokens and an extra draw/play or discard. Something that really ramps up the chaos of his deck.
It's interesting how our perspectives differ, because I saw the damaging base Power as being very important to Parse.
I mean I know there are people who rely on the Wraith for her infrared eyepiece, while I typically go straight for the throwing knives/razor ordnance + targeting computer. There’s no wrong way to do it!
I go for Infrared first because of the card draw, so I can get to the 2 damage dealers faster.
I always find with variants that lose their damaging power that I always run into a case where it would have been nice to have that damage instead. I'd say the one I feel this the most about is Haka. Though I like the Eternal Haka better than the others simply because I have better odds of getting to his damaging equipment cards and while doing so I fill up my hand for a strong Haka of Battle.
Smoke Grenades and Stun Bolts for me. What can't hurt you can't incap you.
Ditto for me, or if I'm feeling very silly MEGA COMPUTERS FOR ALL
There are some environments I bring Wraith into just for that. It neuters the Enclave of the Endlings, Final Wasteland and Dok'Thorath almost completely.
The best variants - in terms of raw power - are pretty well agreed upon: mostly some amalgamation of TL Tachyon, Grandpa Legacy and Hunted Naturalist. I personally think Hunted Naturalist is the best hero in the game by some distance. When he's got a form out, he basically does the work of 2-3 heroes at twice the efficiency.
The most interesting variants are the ones that highlight the less-popular cards in the deck and take them from meh-to-great. Omnitron-U makes Self-Sabotage and Singularity game-winning plays. Felicia Legacy makes Surge of Strength a lot better. Prime Warden Tempest values Otherworldly Resilience and Elemental Subwave Inducer a lot more. Termination Unity gets more milage out of Flash Forge and Bee-bot, etc.
*Sigh* Poor DW Setback gets no love.
More cards for me, I guess.