Basically, Fire spells have always been something I could argue about for days. The short version is, I think Blood Rush is really shitty damage. Since we're speaking on a 12 AP basis, Burning Blood becomes an option, since you can use it twice.
Burning Blood (level 145): 93 Damage + 60 scalding (60 damage at the start of the target's turn) in a cross AoE. On a crit, it's 137 base with 90 scalding.
2 Burning Bloods total 306 damage, in a cross AoE, if you count the effect.
Blood Rush (level 145): 72 damage. On a crit, 103 damage.
4 Blood Rushes total 288 damage, on one target.
Upsides to Burning Blood:
-Better Single target damage
-Scalding stacks with other classes
-You get that cool flaming effect on you
-Probably more interesting than Blood Rush
Downsides to BB:
-dat cost (lose 1 AP lose half your base damage)
-Not hybrid friendly
-Possibility of you not being next to the target at the start of their turn (losing 120-180 base)
Upsides to Blood Rush:
-Doesn't hit allies
-Works well with Transposition
-More opportunities to crit
-Cheaper, easier to finish a weak enemy
opinions are all welcome. I'm probably going to try Burning Blood for a month or something regardless.