I have yet to beat an opponent in PvP with Colossus. For instance, with a PvP rating of 1400, I just played someone with a rating of 1500 who had Colossus and Scarlet Witch. With Colossus's ability to block single-target attacks for 3 rounds(!), combined with Scarlet Witch's hexes and chaos shield, my opponent lost a few hundred off Colossus before my entire team was defeated.
Someone mentioned there are ways around Colossus's shielding ability. Yes, there are the multi-target attacks, which if you can build up enough Attack strength (e.g., Thor's Bruiser & Mjolnir strength bonuses), you can make one big thunderbolt attack. In the meantime, your team gets beat up while waiting for this build up. I suppose if all your characters had multi-target attack abilities, or sneak attack abilities, you can hit others. But the other thing is that Colossus takes so little damage when he is hit. Even Thor juiced up to the max both bonuses and using the Hammer Throw, doesn't make that big of dent in him.
Finally, I don't understand why Capt. America's shield was nerfed to 1 round, but now there is have an even more potent defense with Colossus's shielding ability for 3 rounds. (3 rounds is is too long, IMHO.)
Anyway, if Colossus's shielding ability doesn't get nerfed, Colossus and Scarlet Witch looks like the ultimate PvP combo, which used to be Thor & Capt. America (my current PVP team). I expect to see more of the higher rating players to have these 2 characters. I know that's what I'm aiming for now before I try to play with the "big boys & girls" again. <goes to cry in the corner>
http://forum.playdom.com/images/icons/icon9.png