Backburner was killing him too often, but a 2 ammo per shot Zheitsev is doing nicely. Now’s a good time to farm if you want to try it.
Only trouble is that it’s great on the clone, not so great on Zane, mainy since you have to repair twice for some strange reason when the clone is using it (glitch, I assume).
Love the “debuff” build. Give the Eruption to Clone and give the It’s Piss to the Drone 
. Another fun combo with the Clone is the Grease Trap. The Eruption > Needler too.
I use the clone grenade skill, too. I’ve heard people say it goes off too much, but I’ve not found that to be the case.
Zheitsev has the added bonus that the debuffs are homing balls that deal good damage on their own.
The Eruption is amazing on Zane but you need to do a certain trick with it. Specc OUT of Cool Hand, and while you reload, either spam the Sntl target but or grenades. They cancel the reload and you spam debuff missiles. You can give the Drone/Clone constant 200% multiplative damage bonus
no need to do that at all you can just use it normally without any exploits