Again, the unwillingness to use TBN because of 'DPS' reasons outside of grit is really not true and absolutely not a reason (by itself anyway) to rebalance drks CD suite.
That 6 potency per use (considering a 15 second window is ~3000 potency in GCDs alone ignoring Auto attacks, Blood weapon multipliers etc etc) shouldn't stop anyone from using it. People have just made a mantra of 'TBN is a DPS loss out of grit' and never use it. Its in your mind. They could buff bloodspiller from 400 to 406 pot out of grit and it wouldn't make a lick of practical difference. Think of it as 'TBN is a sidegrade shift in my damage' and suddenly using it out of grit isn't so unpalatable. But that's what it actually is. The DPS loss is virtually nonexistent and shouldn't stop anyone from using it ever.
The thing TBN needs to be effective is to more reliably give the refund so the risk in using it is lower, not a DPS buff to using it effectively. Adjustments to the duration and/or refund requirements is all the buffs. This reminds me of the onslaught stuff when it came out. Everyone dismissed it as a 'never use' skill because it 'lowered' DPS, but its in truth a sidegrade most of the time in deliverance and a buff if used in certain scenarios, but the myth of a 'dps loss' still exists so people don't use it as often as they should. Same for TBN out of grit. Theoretically its a miniscule irrelivent level dps loss. In practice it is a DPS gain unless you end the fight with zero blood. Its a dps gain until you account for the SE blood gain and TBN>Spiller delays that 10 blood gain by 1 gcd. ie: 3 TBN>BS removes 10 blood. If you use TBN 3 times but have 10 blood at the end of a fight it was actually a DPS gain because that blood never got used to realize the DPS loss from TBN. Its only a loss in theory over a VERY long period of time. In reality, it will not affect your parse at all unless your TBN prevented you from a natural BS. EG: you have 40 blood after a fight and used TBN 3x. Very specific scenarios.
Just use it outside grit. Eat it like candy. Stop the mental block of 'its a dps loss'.