Let's not forget that Grit is a worse Shield Oath...

Shield Oath give a 15% damage dealt penalty for 20% damage reduction on damage you take and increased aggro generation whereas Grit is 20% damage dealt penalty for the same thing but does nothing else but hinder you because you are spending too much of 1 resource to try and get a DPS gain but you are only shooting yourself in the foot because Grit restrictions for effects and potencies...

If Grit had Bloodbath effect built into it then it would justify damage dealt penalty as well as removing Grit restrictions on certain effects and potencies, WARs Defiance justifies having a 20% damage dealt penalty by giving you 25% more HP and increased healing when someone use a healing spell on you AND has a skill that nullifies it for 20 seconds

(But you might as well remove that penalty anyway since you would be getting more mileage out of it because you would get more damage dealt and more aggro generation at the same time)