Just for fun, gonna go a bit more esoteric/sideways. Also just a fun scenario because some of these folks make for bad rumbles in arena but work here
Nightcrawler (X2)
Wolverine (comics)
Alex Verus (Verus books)
Chloe Lewis (Freaks 2018)
Predator (Original Predator film)
Domino (Deadpool 2)
Verus in his urban fantasy series is a precog kinda on the level of Nic Cage in his Next movie. He can narrow down possibilities and find pretty much the exact path to get what he needs done. This means he'll be not only navigating to get them the best surprise for the dragon, he'll be able to know exactly what angles tactically to approach the situation in a way only direct foreknowledge would allow. In series he's not invincible of course; gets beat by a combination of raw power, incredibly intricate one-sided planning by the villains, and exploitation of his personal weaknesses. Two of those things aren't going to come into play here and he's taken out his fair share of things way too strong for him to handle in a fair fight with his precog abilities and planning.
Chloe is a kid telepath who eventually manifests power great enough to mind control folks from miles away along with remote viewing while doing so but has no other abilities and would either get stomped by a blitz or by telepaths that can have feats for actually fighting telepaths because she's the only one in setting or stomp opponents. Kind of questionable whether she's street level but technically Cass would take her out in arena I think, so I'm putting her up :P In this scenario she'll basically be able to do what she does best, sequester away and work her stuff from afar. She'll be using her mind control to stymie if not just completely shut down Smaug's ability to respond of course
Predator brings invisibility, some firepower, but most importantly if worst comes to worst he has a mininuke that he can toss into Smaug's mouth, or be used by Nightcrawler to send into a spot Smaug won't like.
The main thrust of the attack though, is really Nightcrawler and Wolverine, where the plan is to use Verus' precision with precog combined with Nightcrawler to find the right spot to have Wolverine just dig in with claws for maximum effect and rip and tear. If need be he can teleport into Smaug for maximum effect if Verus can direct NC on the exact moment/spacing to not be Philadelphia experimented
Domino is here to just add the benefit of luck aura so things turn out right in their rolls in this D&D style adventure
and moral support