He was good in 2009-10, but wasn't exceptional except one series. People were calling him the next Wasim, on potential, not on results. So it would not be fair to say that he is a shadow of himself. With the right conditions, he has shown that he can still be menacing (Asia Cup vs India). But he does need conditions in his favour. On general/average conditions he is performing as he had performed generally in 09-10 period (minus the England series).
He is still a good bowler, possibly one of the best in sub con, but expecting him to be the next Wasim is setting yourself up for dissappointment.
Other sub con bowlers, like Shami, if they bowl well consistently, can take the mantle of the best sub con bowler from Amir.