Asif's a huge talent, you can see how he hits, he looks far better in that aspect than any other batsman in the PSL. Clean hitting. It's no wonder Inzi (and probably Mickey too) want this guy to perform. He's not a pure out and out slogger like Afridi had been doing.
He is also one of the three Pakistani batsmen who have really stood out in the PSLs for ability to score big, accelerate and dominate attacks. The other two are Kamran Akmal and Sharjeel who are not in consideration right now. And PSL is still the closest thing to international cricket for Pakistan in limited overs.
I think people are also being a bit harsh he hasn't had a lot of chances, and hasn't looked terrible at the crease. He's also under pressure to score quick, he's striking over 130 SR in T20s and in ODIs. And yes his overall domestic record is bad, but since he broke out in PSL, he has done well in domestic, list A and recent PSL. The promise of Asif is clearly since that breakout in PSL, Asif's improved and turned over a new leaf thus learnt to perform in domestic consistently now, i.e. something has clicked.