Tbf Sehwag has never been "inform" in 20/20 cricket, his overall record is actually quite poor. Not saying he can't be a very good 20/20 batsmen because this certainly isn't the case, but I don't know if you can put him at the top when he's lagging so much in one form of the game.
Lagging behind? If we talk just CL alone, he made a 23, 66, then 47 and every game DD played in CLT20 he has outscored both Gambhir and Dilshan. Heck his 66 alone just barely outscores both Gambhir and Dilshan's combined runs made in the tourny and he didn't even PLAY the 4th game :laugh On top of that he made most of those runs with the boundaries so I think its been a good T20 comeback for him. Remains to be seen how he finds himself back in ODI's and Tests again.
If not him I would pick Gayle too or even Kallis even though he's been struggling in ODI's for a bit.