Does anyone know how mercenaries' temporary auras work?

Particularly interested in this Trarthan Agility.
The length, how often will they cast it?
Is it similar to Alva's and Huck's buffs?

Update:
Well, I hired her. I didn't think I could kill her, but I did.
Here are the test results:
This particular temporary aura gives The Flow Untethered Buff (same one from The Flow Untethered Unique Cloth Belt). The range is minimal, and I had to stay very close to her to get the buff, so it is pretty useless.

20s cooldown, 8s length. Definitely want to get it supported by greater AoE and greater increased duration.

Throw on some AoE / skill effect time gear and it no longer needs to be all that close. Plus, itll buff nearly every other skill on that particular merc too.