I won't even try to argue the math, as I'm hopelessly deficient in all but general concepts. However, I do have anecdotal evidence of Blood Drain goodness, for what it's worth.
First Boss in HGundrak...healer snake-wrapped (yes, we were trying to just burn him down, for the thrill of the kill), boss still at 5%. Everyone else died, from AOE damage w/no heals...I popped all my trinks, pots, Last Stand, etc. Delivered killing blow, after more than a minute of soloing Boss (my dps is only fair, after all).
Everyone cheering me on, I gazed at screen, as the Words "Blood Drain" faded.
I may change my enchant tomorrow, but, for now, I'm satisfied with this one...
Oh, and, even better...my healer, the one who was snake-wrapped? I cut him out of the snakes, he was dead, so I hit him with my goblin jumper cables--and they worked!! Even bandaged him some..."There, you feel better now, healer?" Mwahaha..
---Note: Apologies, I'm repeating myself, with this story, from another thread...they say the, what was it--memory, yes...first thing to go...
-"Just like a buzzin' fly, I come into your life, I'll float away, like honey in the sun..."--Tim Buckley