Distortion is amazing. Diversipn on the other hand is not. You can't really use it on Champions to keep yourself alive, unless you're already spamming Illusionary Riposte (sword offhand) and cancelling for the daze, in the hopes of clearing Defiance stacks off for when you can hopefully get lucky with Diversion having clones both alive AND ready to reach the target when you need that interrupt RIGHT NOW.
It wasn't well designed before Defiance ecame a mechanic, and it's certainly not one after.
Distortion as a Shatter works wonderfully. The problem is it's often hard to have some clones up to make it work when you need it, in this circumstance, unless you're running Mirror Images specifically for this purpose. When you're being tunnel-visioned by a Champion or a boss, you can't really spawn clones off to the side, they're already in the line of fire. Any residual damage going out is likely to gib them, be it a cleave from an auto attack, a splash from a special, an aura, whatever.
Assuming you can keep your clones alive (which is easier to do when there's no tunnel focus then when they're being "ignored" by focusing on you), the boost to both Ether Feast and Distortion is huge. But can you keep them alive until you need them? That's what I've been having trouble with.