Curse of Flesh rips open Blood Pact a new asshole.
On a side note:
That few turns and using CPB as a strat should this be possible?
To me the kind of damage put out and in such a short time would be more the realm of to next.
Using furious revenge, a few blood pacts, crests, and decapitator basically allows zerks to "burst" out insane amounts of damage in such short terms, i've done as much, even more, and in even fewer turns [around 400damage for a double hit in 20 or so turns], as long as the cards are played right. This is really exclusive to zerks though because of FR. Other jobs can do as well, but not as good as zerks.
Bloodpact draw backs should probably include additional lifeloss in the curse, this would balance it greatly, since it shines so well in long term fights. For zerks though, the initial drawback is hardly noticeable, since the spirit is offset by the willpower you get in the crests and the sigils, for other jobs, unless they're fighting against spirit, it's not really game breaking.