Rastakhan's Rumble Guide
PassiveSpell Damage +3
Does this affect healing cards?
I decided to give this a try with Warlock and it did not affect affect the healing of Drain Life. The new card text was "Deal *5* damage. Restore 2 health to your hero."
-Witchwood Monster Hunt-
Aside from the obvious use of making Toki’s spells unbelievably potent, this can also help Tess quite a bit. Suddenly, her Backstab, Fan of Knives, and Cheap Shot go from low cheap damage to deadly board-clearing spells. Her ability to Scavenge her spells back into her hand can make her spells just as potent as Toki’s!
Does this affect the damage caused by Deathstalker Rexxar?
No, it does not, because it's not a spell. As spell damage never affected SI:7 Agent's damage for example