I finally made it through this instance tonight, and though I won't spoil the story line, I wanted to offer some thoughts on how to survive the final fight. (It'll be pretty obvious which fight that is.)
I regularly run in a 5-person fellowship: guardian, burglar, minstrel, loremaster, and champion (me). We made it to the final fight at level 50 and wiped several times. (One wipe was just because we didn't expect the mobs to notice us quite so quickly as we were approaching for try number two. :-) The next session we were mostly level 51, but more important we added another champion for extra dps and off-tanking, because this fight has a metric ton of adds. And it's no surprise that the key to the fight is doing triage to control the adds.
Some of the adds, especially the two gauredain that start out near the boss, won't come back once you kill them, so deal with them as fast as you can while making sure the other adds don't get out of hand. In our case, we stunned the hunter (ranged attacker), had one champion offtank the other, the guardian of course tanked the boss and did what he could to grab adds, and the rest of us dealt with the adds.
Some adds will show up no matter what you do: normal wolves, signature wolves, gauredain. Some you can prevent. In particular, whenever the boss summons up a wolf totem, kill it as fast as possible. Otherwise it summons still more adds.
The other thing that caught us offguard was a fear effect (as distinct from dread). Conhuith potions removed it, but not everyone had those ready or recognised the effect.