Weird use of gems in battle?

[Squirrelloid]

ok, first of all you're calculating fatigue wrong. Its not halved for every 1 over, its 1/(n+1), where n is Path-Path_required

So 8-5 = 3 -> 1/(3+1) = 1/4 cost = 25 fatigue per casting +spellcasting encumbrance.

Only one gem can be used to increase path level (and thus level dependent effects), so i might expect an extra gem to be used per cast, making that 1/(4+1) = 1/5 cost = 20 fatigue + spellcasting encumbrance per cast, and effective F9.

Additional gems can be used to reduce fatigue cost, but since the next gem only saves 4 fatigue, I can't imagine she'd use it.

How the heck did she get to 42 fatigue before casting anyway? But if she used 3 gems that's 16 fatigue + spellcasting encumbrance to go from 42->70, so she must have a whopping *12* spellcasting encumbrance (ow!).

So, i don't know what's up with gem use necessarily, but I do know you should reduce your spellcasting encumbrance somehow - 12 is crazy town.