Yeah, I was thinking of them from low to high, dunno. The soul stacking was meant for more concentrated item grind, so I didn't take into account the possibility of permanent stacks. Decay over time seems much better.

Looking everything over, I think I may have been influenced too much by the possibility of 'unique mechanics' when coming up with the scythe skills. In my head, it was more of a late-game oriented weapon style that revolved around lots of AoE and CC.

As for Death's Door... I guess it can be modified so that it either a) isn't a unique skill and simply high mastery or b) make it so that it also increases HP regen exponentially the closer you get to death. I'm not sure if either's a good option, though.