Heal is so weak?

What affects how much a spell heals? My First Aid III skill only heals like 14 health points.
At this point, I'm pretty sure I somewhat gimped my character trying to make some sort of weird hybrid build, but the exp rate is so low anyway that I'm sure it won't matter when it reaches OBT.
At this point, I'm pretty sure I somewhat gimped my character trying to make some sort of weird hybrid build, but the exp rate is so low anyway that I'm sure it won't matter when it reaches OBT.