....or it was because performance wasn't the most important factor when determining whether that particular player was having fun.
Why do you keep trying to force your progression raider or progression pvper mentality on other players who may not be progression oriented?
I'm a progression oriented PvPer. I never would have specced into Cloak and Dagger for instance, I'd be laughed out of the damn arena.
However Cloak and Dagger is not only a perfectly acceptable choice for someone doing world questing, it's probably the optimal choice on that tier for that type of content.
Not everyone cares about being the best. It's a wide game with a wide variety of playstyles, a fact which is lost on many of us stuck in the progression content echo chamber.