i like the concept of paying for card draws with life, but i agree with the others that the health cost needs to be reduced.
some alternate mechanics im just throwing it out there-
*sacrificing a creature to get the draw
*reduce player maximum health by # (5, 10, 15?)
*add poison counter to yourself (1, 2, or one for each card drawn?)
*reduce the % to 10% or flat 10 health