In no way, shape, or form is a Rock/Paper/Scissors model used to balance PVP. No class is a “Rock”, none are “Paper” and there aren’t any “Scissors.” You don’t have a counter class. If any class is an auto-lose for you one of the following has happened: 1) you were out geared, 2) you were out played, 3) we messed up game balance.
But why won’t RPS work to balance PVP? As a prelude to discussion, consider that WoW is made up of a collection of PVP sub-games: Battleground PVP, World PVP and Arena PVP. All three must be balanced simultaneously or players will feel the game is unbalanced. No matter how awesome you are in the battlegrounds, and how key you are in arenas, if players three levels under you in green gear own your face in world PVP every time, you are going to feel something is wrong. That is because people expect good performance in one area of PVP to roughly translate to good performance elsewhere. Sure there is a learning curve, but each area shouldn’t be a totally different game with different rules.
So what is a Rock/Paper/Scissors design? Nearly everyone thinks that this means each class is one of the three “types” and can handily defeat one other type, and be easily crushed by the third type. The exact degrees of how much advantage each type should have over the others varies as much as there are people who subscribe to the concept. So for simplicity, let’s consider the extreme: auto-wins and auto-losses.
Now let’s look at World PVP. WoW has stealth on two classes: Rogues and Druids. As a result, their counter classes must be able to find them despite this. That leaves just Hunters (and they barely have the tools to do this in World PVP). So if Rogues and Druids are Scissors, Hunters must be Rocks, and that means everyone else is Paper. I don’t think Hunters will be happy with that setup. In fact, to balance World PVP at all using RPS at least one more class needs stealth and two more need very strong anti-stealth (and the Hunter probably could use some strengthening here). And let’s not even touch on Nightelves, which are a race that grants a limited form of stealth to multiple classes but for only one side! A Nightelf Hunter would end up being a Rock with Scissors’s ability to hide from Paper.
If you think auto-win/lose is the problem, consider if it was just a 2:1 advantage. That is, Hunters would beat a Rogue or Druid twice for every loss. Maybe that sounds okay, but remember that the other six classes (seven in the expansion) will beat Hunters twice for every loss too. If you try and just pick some classes to be Rocks, Rogues and Druids simply hide from them in World PVP or only attack when they can make up for the 2:1 advantage.
And the problem doesn’t end with World PVP. Arenas don’t work with a RPS model either. I’ll skip 2v2 and 3v3 as Blizzard feels those are the least “balanced” already and we’ll go straight for 5v5. There will always be a class that is perceived as dominate in such a competition. Whatever class that is will appear a larger percentage of the time compared to other classes. If that class is Rock, teams with a lot of Paper will beat them. But then Paper gets the reputation for being overly strong which swings things to Scissors. Some teams will try and be balanced, but they’ll be one short. That means for example, RRPPS will lose to PPPSS. And things will just keep changing. The game stops being about PVP and becomes about what team you just happened to bring to the fight. All arena matches are just like the card game War, where both sides reveal their teams and you instantly know who wins.
It is only when skill is why you beat your opponents, not the innate abilities of your classes, that PVP can be balanced. Name any two classes with any spec you want and both should have reasonable shots at defeating each other when they have the proper gear and skilled and experienced players behind them. A lot of people feel this is an impossible goal, and that is why they don’t balance games. As long as you believe it cannot be done, you can’t do it. As long as Blizzard believes Rock/Paper/Scissors is the way to balance WoW, they won’t be able to do it.