Im looking for some info on him. I tried with some ls mates (all 75 but me) and we got hit by howling moon pretty much immediately and wiped. Does he use it a lot or is he just absolutely not melee friendly on this server? Im closing in on 65 and im closing in on 65 and want to round out my avatars but still lack him and diabolos. Also with the rewards, can you claim them without getting the whispers or can you only help? Ive heard it's bugged but didnt know how exactly the bug affects getting the rewards after the fight.

He uses it a lot, highly recommend to mana burn it.

The problem with the avatar fights is that their otherwise 'two hour' abilities like Howling Moon are coded as TP moves here, so you might see it multiple times in a row, or not at all. Manaburning is really the safest route, perhaps pet/SMN burns.

You get the reward KI regardless of having the quest, but cannot turn it in until you are able to flag the quest. Only 1 person in the party needs a Moon Bauble. A single, very well-geared BLM can solo Fenrir, though it does speed things up a lot if you have a RDM or BRD for Refresh and Bind/Grav/Sleep. If not, the BLM can speed things up with Manafont/Vile Elixirs/Yag drinks.

Alternatively, you can do this with a RDM and two SMNs.