Come on Hulk just a few more hours!!! Then you'll be pitted against the Joker, when you beat him (if you beat him. I mean hey the J-man is nuts, so he MIGHT stand a chance if he can get Hulk laughing MAYBE). Then again Hulk might just burn the Jokertoxin out of his system.
Then it's just a smart dino, or a guy in a highjacked "wishes it could bust Hulk" armor. Seriously have ANY of Stark's HB armors actually done the job? I mean sure he does ok for a couple of rounds (and this is when Tony is operating it I doubt Don is going to have the Hulk knowledge to put mean 'ol Green Jeans down), but then Hulk gets a good grip, and either rips off the arm, or the servos wear down, or something.
On the smart dino side yeah I don't see Rex being an issue for Hulk. It's a T-rex (Devil Dinosaur anyone?) with missiles (um Hulk's been dealing with missiles from day one, so no issue there). There was some talk of anti gamma missiles, but the tech is nonexistant even in the Marvel universe (not only 616, but across the rest Marvel multiverse). In other words if Stark couldn't design it in all the times he's had to deal with an enraged Hulk, and incorporate it into an HB armor then chances are Mr smart dino can't either.