I feel like maybe part of the problem is that I was using my ult to initiate, so once I went in with E, W, Auto-Q, I was basically just a big purple punching bag for 10 seconds. My build also didn't incorporate much CDR at all, only CDR i built was ghostblade.
The best way to do his combo is to go in with E to silence, Q and an auto attack, then ult. The ult will finish when you do something else, so you can hit with the W at that point, which will bring the blades back in. By that point they're usually dead. If not, Ignite will finish them off.