If he can't play outside, then yes the pick was a waste. I haven't watched the tape, so I don't know how bad his tackling really is, but there are a lot of corners out there who are not known for tackling prowess. If he can cover well enough that QB's throw elsewhere and make plays on the ball when it is thrown his way. The NFL seems to be discouraging tackling receivers these days, so do what is needed to stop him from getting the ball.