I believe the adrenaline is so the opponent's monsters will attack more on your voodoo doll.
If the oponent has really really low attack that he won't reach 100 damage till the end of the game, then you can adrenaline an oponent's creature. The first one, though, will go to the voodoo doll 99% of the games, so it regenerates 5x purify counters per turn (10 per turn per purify).
By the way, here is the other 1%:
I guess it would be better change mark to
5 purifies cost 10
3 adrenalines cost 12
95% of the games, you will only need 1 Adrenaline (for the doll), so you will need more
than
. On the other hand, you need 4
pretty early, so it's also an option.