Whether you should use Thanos at 200 or 300 depends on what else you pull - if you pull the right taxi for him, it's more than worth it to lose his first three clicks.

I used Thanos and Nebula at the qualifier in Austin, and if it hadn't been for a critical miss at the worst possible time in round two, I could have easily gone 3-0.

How effective was his gauntlet/tribute in effect? It seems like it's either your little guys talk 1 or your big guy imperv/invincible it

Pretty well, actually - there are a lot of characters who have no reducers and lost something useful if they get dropped off their first click, so it can be a real Sophie's Choice for your opponent.