The new 2.4 combat log events, SPELL_AURA_APPLIED and SPELL_AURA_REMOVED would benefit greatly from having the src* fields contain data about the player/mob that applied the aura that is fading or has been applied.
The rationale is that it would make it much simpler and less taxing on the client for the construction of addons that monitor the debuffs on mobs.
EDIT: This request is primarily for those spells where it is 100% unambiguous to deduce. In my example, I used Corruption. I would NOT expect this to work for things such as the Tree of Life aura, or Paladin auras.