Going by history, population versus population in zones, history, the whole works. If PVP were at pre-I13 participation levels? I'd have a harder case, I think, in saying it's this wholly unliked by the community in general (and saying this as someone who *enjoyed* it, too.) I don't think I'm on anything close to shaky ground by saying it. I'd love to be wrong, answering questions on "where are the PVP zones, I want to take my character there and fight!" in help and the like. If people were seeking it out, there'd be *some* conversation on it. I think I've seen one person ask *if* there was PVP in the game in the last year. The amount of time I'm on is not inconsiderable, and I tend to watch Help while I am (as well as LFG for spillover there.)
And yes, part of the issue is that you really *do* have to learn to play a vastly different game. As a tank? Get ready to get mezzed. Healing? Watch it not work the same. Control? Eesh. But if the *demand* were there, people would be asking about PVP builds and just basic questions, as well. There'd be other people around in the zones. People would be looking for the arena. Those questions just don't come up.