Not sure if it has been mentioned, but if you had a tank that was getting a lot of poison stacks and other debuffs, that last fight is a little harder on SCH than on WHM since I believe SCH doesn't have something like WHM's Esuna, yet. I've had scholars easily heal the fight, but usually that is with competent dps and a good tank who knows how to dodge and try to avoid damage. From what you wrote, I think it was mostly a tank issue, especially since you did it with the replacement tank ^_^v