I have been lurking there for a long time, but first time posting. I have been trying to make Iron Man work since vanilla. I thought he was pretty decent in vanilla, and I was looking forward to some new combos and stuff with he buffs but only the found out in UMVC3 he sucks some serious ass, so I am seeking some help.
I run Iron Man (uni beam), Dante (jam session), Strider (vajra). I generally follow the footprint of flying and unflying around with air h and s, dropping smart bombs, and uni beam, attack with box jump s whatever is possible. I use Strider assist for defence and Dante assist to extend combos.
I am having a lot of problem against fast moving rush down teams and characters have strong air moves like Nemesis(with good assist backing him), Zero, Dante, even Hagger (behind strong assist of course) with his godly pipe with Iron Man, I struggled to do much even with all my assist available.
Let say you have a Magneto tri-jumping towards you, I find there is very little Iron Man can do to fight back, or run away to ease the pressure little bit. His air h is good at controlling space in front of you, but it doesn’t hit high or low enough to stop Magneto rushing in. Repulsar blast is useless outside of combos and his air dash starts off too slow to get away or to pressure him back and I get air throw by him a lot while trying to get away. Starting offence is hard as well, because Magneto is much more mobile than you and super jump ADDF h or s is too predictable and slow, in my opinion this is free air throw for Magneto all day and chicken blocking beats Iron Man for free 
I understand this is a bad match-up and Iron Man has no defence against rush down and little tools to generate some offence of his own, but there must be something else I can do consistently, other than get lucky and land a random hit and TOD him.
Another problem I have with him is sometime when I land a box jump s, it is too far for him to land a crouching l or crouching m, stand h, into launcher. Is there any way to fix this or is there a different ground string I could do to land a combo? How are you suppose to land a combo from crouch h into flight, air h unfly, falling h, when they are far away and only get hit by the tip of the beam? I don’t think only crouch h into air h is enough for defensice zoning and to make people respect Iron Man so they won’t rush in recklessly so I am get a chance to actually play.
I don’t really want to change character because I really like Iron Man, he looks and play like a cool character, his combos are sick and Proton Cannon does some serious pain, but he is probably in the bottom 5 in this game. If they leave his air dash alone I think he would definitely be in the upper tier by now.