I think it affects spells working to a degree as well, I know some potions will fail for example when it is thick. Not every time of course. Just like when it is thin sometimes you cast and it costs no mana. I don't believe it has any direct affect on damage from spells, but I could of course be wrong, and it didn't seem to be more dam reduction or anything for resist. Critical did not seem affected, nor did discern spell. And spell evasion always fired like crazy so I never noticed a difference. Maybe spells are more easily baned to, I haven't played enough ragers to really say. Just meant the most noticeable thing I saw for ragers was better duration of powers. Vets probably know a lot more than me on this.