The size comparison of the mapping in FF14 and the mapping in WoW is a little too vast. WoW is built specifically for both PvE and PvP, while FF14 is built specifically for PvE, with PvP being put to the side with its own series of modes. If you were to enable a PvP server, then you can forget about making any progress, as the areas are far too small to have anyone not resort to camping entrance points (intentionally or not), as any other part of the map is sprinkled with monsters. The fun is taken out of it, when you feel like you're being spoon fed handicapped situations, no matter where you engage a player from.

You could argue the exception of Heavensward. But who would make a PvP server, just specifically for a portion of what the game has to offer?