Just tossing out two ideas I'd love to see implemented on my main class:
1. Remove the Grit requirement for Souleater to lifesteal. This wouldn't break anything at all, but it would be very helpful when soloing out in the open world. Also, it would help in pvp.
2. Allow Blood Weapon to work while Grit is active, but make it generate tp (at a very reduced rate) rather than mp. This is only while Grit is active. It would still generate mp when Grit isn't active.
If they made those two changes, DRK would be my favorite class from any MMO since FFXI.