Didn't do all that badly, all things considered. It surely could've been a lot better -- my control of the fight was a little off, which resulted in a few near-wipes. Switching focus between dotting up the boss and keeping an eye on his actions (where he places the little field of death magic AOE) was my biggest problem. Keeping myself alive during "oh shit" moments was problematic, and even impossible at some points since I'd only spent points in Reaver -- I've since loaded a few points into Paladin for extra "oh shit" hotkeys.
I noticed the boss also switched targets quite a lot... I presume it's standard boss behavior to switch targets & hurl random spells or AOEs (in the case of this boss) at ranged attackers. I could be wrong though... I'll have to pay closer attention next time and see if there's some kind of threat meter or something.
Overall, fun times. More practice is definitely in the works, though. ;)
Also, yeah, I did have to switch back to the game's old renderer again. I love the game's detailed graphics engine and all... but I enjoy having a stable framerate, too. ... which is something I never thought I'd say with this computer.
( Random bonus! One of the first screenshots I ever took in Rift. )