So, been testing out Harbinger and I'm probably missing something, but is there a reason the vamp regen with the Mortality Hex isn't made like the ranger blood thirst?
As is, it will not stack with e.g. a lesser nine lives stealer or dusk - instead it will use one of them (at least on the PGCC), seemingly at random. Also, the vanilla vamp regen is limited to once per flurry instead of one each attack.
When you curse your weapon, the bonusses do not dissappear when you drop it to the ground - making it hard to get rid of the bonusses when leveling up to a new and better tier. It's more an annoyance than anything particularly problematic.
