I was wondering about the 8 sec Blooddrinker buff from a Hallowed Fang component. If I apply the buff and then cast Grasping Vines, do the vines also have the 25% chance to do the extra bleed?
Only if your skill has Weapon Damage (WD) stat in it.
it is a flat damage bonus, so as USer Bane 845 wrote, it only applied to skills that has weapon damage.