I have always killed him with Arcane as it is my normal raid spec. The 40% threat reduction is very helpful.
However mana is an issue and I often find myself wanding him the last 5% - 10%
I plan on trying Frost (very high DPM) next time we kill him as we are trying for hard mode (no saronite vapors).
Since Fire and Arcane are pretty close in DPS and DPM I think I would run in to the same mana issues with Fire. And I would not have the higher threat reduction. So I assume Arcane > Fire for GenV.
hey man got a quick question. do you prefer to spec arcane for general vezex for the 40% threat reduction..? or fire with the -10% threat?