As far as I know the ability affects her, I haven't actually looked at the numbers, I just assumed it was working.

As for allies though, given oaks ability that uses that wording it does mean creeps and other DG. However, I don't think creeps actually use "abilities" just their auto-attack. 

That's actually what I was thinking about, Priest casting. Hard to characterize that as an auto-attack, it seems more like an ability that is cast, with a corresponding cool-down time. There may be other grunts that have abilities, too. Miyamiya assumed that this effect worked on Sedna and I assumed otherwise, but neither of us have tested it. Wonder how hard it would be to set up a test to see. The reason I ask is because after I get Heal, Inner Grace, Pounce, and Healing Wind maxed, I'm not sure whether to take Magnificent Presence or Yetis or something else, and the attributes seem to be only applicable to the Yetis.

The ability to reduce cooldowns effects her.  You can easily see this by checking what the cooldown of her abilities is (via the skill screen) and compare it to what value you see when you mouse over the skill.  It is however rounded (I don't remember if it is up, down, or closest though).

As for the usefulness of the skill.  I've been theory crafting using it with that favor item that also reduces cooldowns, and then team up with Erebus to be able to almost completely stun-lock an opponent (Charm + bite over and over again).