Arcane Backdraft (Rework of Arcane Backlash)

[Zaydos]

Maybe make the requirement
Full BAB +3
3/4 BAB +5


I might make a special part of it that says that the damage dice can't exceed the number that the caster uses... That way a spell that can do max 15d6 cast by a 19th level wizard won't get 19d6 sent back at them

Don't have Full BAB and 3/4 BAB prerequisites that are different. Doesn't mesh well with 3.X in general and makes multiclassing a Wha?

As for the other you may want to consider that but also amend that it is only true for spells that deal damage.

Really though if they're using a Reflex half spell and only hitting one target they're making a mistake as it is.