I agree with NeoSeraphi on the d8 HD. Not sure about the 3/4 BAB, I'd probably leave that at 1/2. Maybe give good Fort though.

I also think that Blood Mastery could be spread out among the levels. Con-based casting from the start should be fine. I'd probably move the stench thing down to 19th, just to kill that last dead level. The other effects make a fine capstone.

I think somewhere in there should be an ability that lets the blood mage use damage it has taken previously in the round to fuel and/or strengthen spells. And maybe a higher-level ability to let them sacrifice the blood of others to fuel their spells.

All in all looks cool though. Good job!