If you break TBN 15 times in the fight, you have generated enough bloodspiller Gcds to lose a blood spiller generated from 5 soul eater combos. At this point it is definitely a loss.

A naturally generated bloodspiller from soul eater is a much higher gain. Even if you assume TBN "breaks even" in dps, after 15 TBN you definitely have lost a good chunk of potency and it is definitely marked as a loss.