The idea that the glow represents a completed set has been proposed by some.

Good observation on the barb :) . It could be a randomly wandering townsperson, like the rogues in act 1, though it seems odd that they'd add that (as the barbs are supposedly all out fighting, or dead). Or it could be a merc (as z disables the little icons at the top). It's an axe-and-sword wielding one, though, and it seems very odd that they'd allow those now, what with them looking different and such. I'm really not sure what to make of that...