Shadowfang
Arcane
In the Infinity Engine games, improving your spell damage in this way would have been pretty pointless because they did so much damage already. 6D6 damage fireball? Why would I want to pump my Might to add a few measly extra points of damage to that? I would rather increase the area of effect size.
Actually, generally speaking, damaging spells are not as important as crowd control spells in these games. Pump your Int and get a Hold Person spell that takes an enemy out of the fight for a long time.
I would agree more with you if we had any notion of how much damage spells will do. If indeed you are right then you just found the dump stat for a mage.