As I've commented on other threads, and is a very similar sentiment to that expressed by the OP:
Vamp and WW should both operate as optional skill lines that you can mix and match with other skill lines, no different to any other skill line in game - with the possible exception of being 'cursed' with either of them would leave you slightly vulnerable (as vamp already has) and changes the 'flavour' of other skills (e.g. sorc summons a bat companion instead of a winged twilight).
But yes, you shouldn't have to build around that 1 skill line in order to create a useful build, rather there should be several ways to utilise the skill line in new and interesting ways.