I'm thinking that level 4 skills generally should be Tier 2 and so require 2 points into the appropriate school, so add that in, and this seems like an okay nerf. It would certainly help discourage some of the jack-of-all-schools stuff.
Fireblood is one of those skills which I never use, because the idea of enemies bleeding fire never seems all that useful unless you have no melee units of your own to get caught in the flames.
