The Vampirism blessing is either bugged or is lying to you in the description

[Karsh]

I quote: "Whenever you hit enemies, restore life."
Afterwards: "Lifesteal on Hit: 3"

But this blessing doesn't work 'on hit'. It instead works just like all the other 'chance-based' blessings, in that it's ON ATTACK, UPON FIRST HIT OF IT.
In other words - it's limited to healing you just once per attack, NOT once per hit.
It's not "Whenever you hit enemies", it's "When you hit your first enemy after attacking"

This makes this blessing MUCH weaker than it seems to you at first when you read its description. In fact, out of all the Legend-tier blessings I've encountered so far, this makes Vampirism probably the weakest one so far.