NIGHTBLADE, SIPHONING ATTACKS

Apostol

Does not work to restore 4% Health with basic weapons(tested with bow and dual weapons) attacks.
Proof: http://youtu.be/LICT622k5aU

Aedh

There's a tooltip bug. Siphoning Attacks is not supposed to return health.

If you want that, you have to pick Leeching Strikes (and even this one is bugged, as it gives 2% hp instead of 4%).