[Bananadine]

And, particularly: precision is only for things that can VISIBLY miss. So if you SEE your dudes shooting toward the wrong spot then their precision may be too low and maybe you should give them a precision boost or move them closer to the enemy or stop casting Storm or something. And if you didn't personally see the projectile or spell effect hit the wrong spot then you don't need to worry about precision because it wasn't used.

Boost penetration if you have a special need to beat magic resistance more easily, and don't if you don't. I guess. It's hard to tell how penetration is working, except when you're testing it under controlled conditions, which of course never arise during ordinary play.

I'm not sure whether precision matters for spells like Body Ethereal or Freezing Touch that have range 1 and no explicit precision stat. I don't recall ever seeing one of those spells miss. If they do ever miss, then I suppose it happens so rarely that it doesn't matter much.

Penetration is often not about "how much" damage is done. Consider Nether Bolt, which appears to pass a magic resistance check (penetration matters here) and then, if it passed, do some damage whose amount is determined by the spell's damage stat and by the caster's skill--and not, I think, by penetration.