Siphon bullets make sense as it only offers you sustain and not allows you to deal more damage. Inhibitor gives you survive ability and cc which is also vitality traits. Shadow weave is both utilitarian and offensive so he can be swapped back any moment. Vampiric is only viable is you already build damage and have a character suitable for it and active gives ammo + firerate, which is weapon stats traits so his placement is adequate and swapping it would only make it stronger as its users will have one more weapon slot. Only thing by which he can placed in vitality is lifesteal, but they will have to change stats on item and active for that.
