Personally if they could just find a way to make blood our DPS resource and MP our Mitigation/HP restore resource, I'd be golden but it would require some rework... Have dark arts transfer MP to blood with a cooldown and delirium transfer blood to MP with a cooldown.

TBN as a standalone cooldown with no benefit/cost beyond the shield @ 30 seconds would be neat too though, I'm guessing darks would use it more.