Resist magic, poison, and disease. Poison and disease are powerful against ragers (especially rager apps). Magic is a no-brainer. Plus stoneskin.

All of that is priceless for a rager.

Also, the bonuses of a svirf rager over a svirf invoker are not equal. Rager, with resist, with stoneskin on top of that, is sick. I've fought enough to know.