We are currently working on this fight and although we havent quite got it yet healer mana hasnt been the issue.
I play as Disc and don't have too many issues with mana - your ideas are pretty much what I do. We use a warrior MT and have no issues with using cooldowns such as Pain Supp, Shield Wall, Hand of Sacrifice, etc..
For the mana regen you need to be getting the max number of stacks you can take - for me as Disc I can stay in for 7 debuffs with a PW:S on and loose half health when coming out - you need to make sure you dont get any more though! You can then get about 5 more stacks after the first set wear off before the Vapour despawns if you are quick enough.
Rivers know this: there is no hurry. We shall get there some day.