I think that there should be a PvP tag for World of Warcraft, wow-pvp or world-of-warcraft-pvp. There are currently 77 questions regarding PvP in WoW, showing that there is a lot of interest. In-game, PvP and PvE require differing approaches, meaning that a question warrants a different answer in a PvP context than out of it. Also, I personally have wanted to use such a tag but, seeing that there was only a world-of-warcraft tag, I was forced to clarify my interest in a PvP-related answer in the question title.
I see no problem with a world-of-warcraft-pvp tag, as it is a well-defined subset of WoW at large.
Do note, however, that if you were to use it, you would still need to include the world-of-warcraft in all relevant questions. (Similar to minecraft-redstone and minecraft)
