Tainting Auras

[Necessitysslave]

Several places throught the forums it states that +X damage/elemental damage/anyother form of damage doesn't stack with spells/skills. but +X% damage does (so you need to be doing the correct damage type already with the spell to effect it in this way)

However I am wondering if you can taint an aura spell with %damage to health %chance to stun and all of the other % based abilities.

What eq could you use to boost the effects of an aura? What are the maximum effects you can stack on an aura?