Mega Charizard X is probably the best (at least fire type) dragon dance user, being very bulky and having a fantastic offensive presence. It even has reliable recovery in the form of roost.
Cons:
-It'll take up a mega slot, so if you already have a mega planned, you've gotta pick one or the other.
-Switching in before mega evolving, it'll take 4x damage from stealth rock, aka, half it's HP, which is pretty crippling considering how common stealth rock is and how much it relies on its bulk.
-It's often seen as a bit overpowered, so if you really care about that sort of thing, it's something to keep in mind.
Darmanitan is one of my favorite bulky fire types as it can use belly drum in conjunction with sitrus berry to maximize its already excellent attack stat and still remain mostly intact. It has fair defensive stats and a good defensive typing in pure fire. Although personally, I think the best part, what sets it apart from other bulky fire types, is its amazing ability, sheer force. In case you're unfamiliar, sheer force removes additional effects of a move and boosts its power. This means amazing options such as a boosted hammer arm that doesn't drop speed, superpower with no stat drops, take down with no recoil, and best of all, sheer force boosted, STAB boosted no recoil flare blitz at max attack from belly drum. Literally anything fears it. c: Zen mode is also an interesting novelty, but it isn't worth the opportunity cost of sheer force, and it swaps its physical and special attack stat, a move building nightmare not to mention making belly drum worthless. Use sheer force instead.
Cons:
-it's a little slow. It'll outspeed quite a bit, but not everything, and no speed boosting moves.
-It isn't THAT bulky, and if you really have your heart set on something that can sponge hits, I'd recommend Mega Charizard over Darmanitan for sure.
-no recovery outside of RestTalk. Not fun.
There are definitely more options than this, but these are my 2 favorites!
