I'm liable to try lowlife reap juggernaut. Should be pretty wacky.
Seams more to be for pathfinder with needing to use flasks all the time to keep life above half. Some pathfinder caster with pain attunement.
I never even considered pathfinder, and I don't get why you are? The point with lowlife is to keep your life just below half so you get the pain attunement damage. I picked jugg because it's the tankiest and none of the ascendencies are well suited for scaling reap as far as I can tell. ES trickster is probably better, but I've never managed to get good enough gear to make ES good.
Scion(trickster/glad) might be a good pick too, since all the nodes you want (shadow and marauder) are on separate sides of the tree, and the fact that scion gets life nodes and +phys damage cluster right at the beginning doesn't even make her annoying as league starter for this. I'm really wary of the low survivability though, and none of the shadow ascendant nodes really do much either.