This guy is virtually impossible to solo, IMO. Not only the self-healing is insane, the amount of damage he does with the scythe is also quite threatening (damn cheating double-damage bosses in Factions and Nightfall..). A 55 build should theoretically work, but you need a LOT of damage output.
Keep in mind that hexes are removed very quickly when he's in Avatar form (so a 55 + Spoil Victor doesn't seem to work). It helps A LOT if a good ranger can Distract the "Avatar of Dwayna" form continuously -- then you can also use hexes like Spoil Victor etc. when he's not in the Avatar form. Otherwise I think the guy stays only 30s in non-Avatar form.. Good luck trying to wear him down and outdamage his healing in 30s..
Since it seems so tricky to solo the guy, me and my friend(s) went directly onto duo (and trio) farming: the two key players being a ranger with Broadhead Arrow and Apply Poison and a warrior/55tank to soak the damage. Conditions work well on this guy, as he has no condition-removal even though the boss regen and the self-healing spells are compensating very well for that.. Keeping him dazed helps a lot with interrupting many of his self-healing skills.
Alas, after killing him more than a dozen times with the duo team as suggested above, damn scythe didn't drop for us, not even once! (yes, the heroes/henchies were far away, greyed out). The irony is that we had 3-4 greens dropping for us from the two other bosses there in that little fortress, while we were clearing it with heroes/henchies..
