I too was disappointed to find a lack of blood magic, and also a lack of spells in general. However, there are two 'rate limiting steps'.
Firstly, the inexplicable 8 skill limit. With only 8 slots, having awesome spells like crushing prison, mana clash, cone of cold, petrify, tenpest etc etc would be largely wasted. It might add some replay value, however. Seriously, DA2 worked fine on consoles, and a 12 skill limit, as mentioned above would surely have been ok here as well?
Secondly, the lack of customisable attribute points. Sure, you can craft some +con armour, but for the most part, a blood mage would likely be all glass, no cannon.
Still, I enjoyed my first mage playthrough. Just saddened by the seemingly arbitrary limitations. I'm sure the devs had their reasons.
And that's enough for you?
I agree with the rest, but I don't really care about the reasons, I care about the results.
And yeah, I had some fun doing one playthrough as a Knight Enchanter. Although this was my first PT, so even if I didn't particularly like the gameplay and felt that it was too bland and uninspired, I powered through to advance the story.
I played a bit as a Rift Mage, the gameplay was slightly more fun, do to stone-fist mainly (why the hell is stone fist a a specialized elite spell all of a sudden? Is this part of the war on fun?) but quickly got bored.
8 ability limit really did a number on your options, considering you had to waste points on unwanted crap just to get to the slightly less crappier spells.
Necromancer I didn't even try myself, just played through Dorian for a bit. Causing chain explosions is fun, but the SP does not really have the huge crowds for it to work well and be effective. I could kill the mobs faster if I don't wait for the bomb to activate. And when you go against a Dragon or any other boss? You really don't have anything effective to use.
Loot based gameplay is really annoying for a couple of reasons.
But the funny thing is, the Mage had an option to tell Cassandra at the start: "I don't need a staff to be dangerous."
Well sorry to burst your bubble, but yes you do my friend, yes you do, because all your spells are X% damage, and X% out of 0 is still nothing...