I'm basically with DemoBytom here. I'm nearly always inside the same bubble as the mobs I'm attacking, or just outside. It stops them following me around and leaving the bubbles. Because of that, Zei's is rarely going to get it's full potential.
I've been using Trapped, Toxin and Iceblink, mainly because I don't really know what else to use. I was considering Zei's, but as I say, I won't get everything out of it.