I think, they halved the effect of guerilla because of those heavy sneak attack bonus damage attacks, because guerilla improves those attacks even more.
I guess my problem with Guerrilla is that those heavy sneak attack bonus damage attacks and enter-combat-with-sneak-attacks are really the only things benefiting from Guerrilla, which makes it seem lacking.
The problem with Touch of Frost remains: Its a Hydrosophist Level 10 spells. A Water mage mainly supports or freezes anyway, so I'm not sure, which attacks would really profit from 5% freeze chance.

True enough. My instinct was to put it at Rank 5 or 7, but I moved it with 10 to match the others. I was thinking that it might also be useful for hybrid characters.
I know, that you meant also damage to magic armor, but it would be still be a bit unreliable. And attacking your self just to get more AP? Such an attack would cost 2 AP aswell, another AP to replenish shield or health, so hardly worth. But cleansing electrified surface can be have tactical purpose aswell. It is surely an idea, that is would bypass the magical armor.
Yeah, more good points, I crossed out my idea and replaced it with the cleansing surface one.
Regarding Made of Stone I think the synergy could be good to make the other talent more appealing.
Hmmm. Okay I guess that would make sense too. Made of Stone does only protect from physical damage so there's still a vulnerability to make it somewhat balanced.