Hmm what level do wizards get stoneskin? Alternate source you say? The next time I should turn down stone skin and say "no thanks please keep your DR10/adamantine for 1 min level at 10 points of dmg absorbed/level, give me an energy resist instead, i'm packing Angelskin.".
Last i heard there were many enhancements and a deluge of items giving damage boosts and raising the DC of spells, does that not count as "spells deviating" ?