King, if you're building AP then you don't and I mean DONT build crit.
If you've started to build AP go full AP, you'll get more damage and life steal from your Q from it.
If you're going to go crit then pair it with AD so then you rely on your basic attacks and your W rather than your Q and a little of your W.
That's like being offered a gun that can one hit, a sword that can one hit or you can choose both that takes 3 hits to kill someone and you can only use one at a time.
Clearly you're going to choose either the gun (AP) or the sword (Crit/AD) rather than them both
Also you basically use the E to clear out a minion wave if things get a little hairy or after you've slowed your opponent.
Tl; dr: You use E to push most of the time and Ap/ crit warwick is a horrible idea. Build one or the other.
Last edited by RedPanda; Apr 30, 2015 at 03:26 PM.