The one change Dom2 really needs.....

[Boron]

Hm perhaps you could make all hoarding items like clams horror marked and aditionally to this diseasing the wearer .
Then you can't be total sure that they pay off at least in the long run and need black servants or similiar to carry them .

Otherwise it is i think too hard to balance them because they become either totally cost ineffective or are still a good choice .

I am sure you have this in mind but i would like to see which costs you think of for hellswords and soul contracts to compare them with the other lifedrain / hoard weapons .