As you said, you stopped to drop Grit for the great cost of MP... For how the stuff works now, drop Grit to use blood sword is useless, since you will almost spend what you got to enable Grit again...

We NEED something else to get back MP.... What is fun on DRK is that we can use dark arts.. But right now, in long fight we can use it just sometimes, or we will ruin all the MP and will need "long" time to get back...

With my little tweaks, should be possible, since i dont ask to change big stuff, just few (remove GCD + reduce MP cost OR allow use BS in Grit + damage increased while BS)