my equip gives me +7 sk, which would get Hex: Siphon to lvl 8 (with 1 hard point in it) meaning ---> +9 life / mana after each kill. Is that good enough or would you spend some extra points?
You never put extra points into hex siphon because engorge adds more per point, if you ever cast it, its +1 either way. But in general you're better off dumping extra points in bind demon for extra damage than in hex siphon, after the 80 for fire skills + blood oath