@Roninbarista: I wonder how much easier your playthrough was - I never touched blood magic in either game and I didn't find them difficult at all. So I'm not sure it was any more of an "advantage" than say... Force Mage or Spirit Healer...
I used it in DA:O. It did offer some serious crowd control, as I was able to immobilize many foes, and my team was able to do some damage to helpless foes. I did a playthrough in DA:O without BM, and entropy worked just fine as an alternative to immobilize foes.
I tried blood magic in DA2, but didn't care for it, and respec'd it for spirit healer and force mage. I played more of a support mage with a some damage abilities.
EDIT: I will say this, no one seemed to care that I had BM in both games, despite calling other people out on it. That never made sense to me. Hawke makes some noise about Blood Magic himself, and could potentially be one. It was rather jarring, and somewhat not worth condemning people for things I was using. This BM became less fun to use in DA 2. Entropy allowed me the crowd control in the game along with support and damage.