Huh, I must have gotten lucky on this part with my engineer. I am playing veteran and just beat the arena of slaughter last night without dying. Although I do *love* my unique ice cannon! I just ran around with my forcefield always on, blasting away. The final round took some time, but everything eventually died. The damn trolls in Act 3 are what have killed me the most. I swear they have instant kill or something.
Well, you're a tank, which helps. The arena is all about endurance. Both this and the lightbulb arena sucks for Embermages.
Thunder Locus, Blazing Pillars, Prismatic Bolts, and then run like hell while liberally applying health pots. That's how I got through it. Oh also, avoid those stupid flame bursts; getting through this place has as much to do with avoidance as it does anything else.