When pairing up to train a lowbie, wouldn't the best partner be the Avatar? That skill that increases XP gained while paired up, does that also count for the partner unit? Like a Donnel/Avatar pair, will Donnel also get +50% XP?
I can't look at the exact wording now, but I'm very sure it's something like "the avatar receives 50% if ...". I've also tried pairing up the avatar with another char and it didn't seem to give more exp.