There's two real skills that T20 batsmen should have. Power, the ability and the hand eye coordination to hit boundaries easily and on instinct, the other skill being able to rotate the strike and pick up the singles.
You don't need as much concentration or technique (or at least technique doesn't help as much) as you do in tests. But having the two above skills isn't so important in tests, you can play tuk tuk pretty effectively.
Asad ain't a T20 batsmen. He's more a consolidating one. He's not able to go guns blazing, in the zone batting. Just isn't his style. Misbah can't rotate the strike well, but he can rack up boundaries when he gets in pretty quickly. Umar's a good T20 batsman, so is Afridi (though would probably be more worth higher up the order). Hafeez is one who does rotating the strike and hitting boundaries kind of ok, but nothing that exceptional. He's an OK one.
Hammad haven't seen enough to make a judgement. Malik is a close to perfect one in domestic, but doesn't play like that in internationals for some reason.