Gamespot posted a playthrough video of Marvel Heroes, complete with developer commentary, and it's a doozy.
The video portion follows Deadpool through an instance called The Raft -- a giant ocean prison tower. While the combat isn't too sophisticated, it's cool to see scripted events and impressive entrances made by enemies. Later on, the devs show off a public zone where Iron Man blasts through hordes of enemies while encountering Daredevil, Storm, Wolverine, the Thing, the Hulk, and the Scarlet Witch.
If you're looking for a superhero-slant on Diablo-style gameplay, then give this video a watch and see if it might be right for you.