No-one could have predicted this. Ghostcrawler, Just Now:
Exorcism can no longer be used on Players
We made a change in the 3.1.1 patch to prevent Exorcism from being used on players. We didn’t announce this change ahead of time because we were trying to get the tooltip changed at the same time to reduce confusion. We still plan on getting the tooltip updated ASAP. Exorcism’s use in PvE has not changed at this time.
Going with a “not on players” solution is not ideal and we will be re-designing how the ability works in a future patch (the plan is sooner rather than later). We don’t like for PvE and PvP mechanics to work differently when we can avoid it. We also don’t like for a major damaging ability to be excluded from the PvP game. However, we thought this had become a balance issue serious enough to address at this time.
We shifted around paladin damage for 3.1 trying to increase sustained damage while reducing burst damage. Unfortunately, the Exorcism change did the opposite. Instead of stealing a GCD from a paladin, it actually gave them an extra one. A Retribution paladin could use Exorcism to cause damage while closing to melee and then be ready to go with their melee damage attacks. (Exorcism of course is not limited to Ret paladins either.) We changed the way paladins do damage for Lich King, so while it is unfortunate (and we accept full blame), it also isn’t too surprising that it is taking some effort to get their damage in the right place.
In the same patch where we remove the “not on players” limitation for Exorcism, we are going to change the way paladins do damage so that their normal combat moves have more depth to them instead of just using abilities every time they finish their cooldown. This should make causing damage as a paladin more interesting and also less bursty. While we have some ideas on how to accomplish that, if you have suggestions or your own ideas about how this could work, this would be a good time to share them. (As examples of abilities you don’t just use whenever their cooldown has finished, you might look at Conflagrate, Brain Freeze, Rip, Overpower or Arcane Blast.) We do request that you don’t fill the forums with posts of limited content or insight about how you don’t like to be nerfed. Nobody does.
It is always a judgment call about when a fix (a buff or a nerf) can’t wait. Some things we can’t change easily in hotfixes or small patches, and some things we consider too risky for technical reasons or for their potential effects on the game.
For those counting, Exorcism remained in 3.1 deployed form for 1 week.
The forum outcry demanded it and so shall it be, though even the most optimistic of us could see it coming a mile off. Ironically Paladins will still have higher burst (which I'll arbitrarily define as damage within the space of a HoJ) in 3.1 than 3.0.9 even after this nerf, and Ret will still tear poor players a new one. As for the rest, we'll see just what happens. Most obvious changes are to fill the Paladin GCD-space with low-damage, low-cost spammable abilities, changing Exorcism to be Lava-burst like and make Paladin abilities require set rotations for maximum damage (i.e. one ability leaves a debuff which then must be used in x seconds etc.). Or... the spectre of Dual-wield.
Spare a thought for Holy aswell. Of all healing specs the Holy Paladin has by far the fewest offensive potential in PvP, at a time when even abilities like Holy Fire see action in top-rated PvP. Their healing abilities remain strong (though not nearly as strong as the 3.0 promised land) and it will be very tough for them to assert themselves in the new Arena Season as we move forward.
In this quest Blizzard will be hampered by the paladin resource system (Mana is a poor choice when you want to prevent front-loading damage), and more worryingly from a PvP perspective a Ret Paladin without front-loaded damage is a poor quality Arms Warrior. This is going to take time and considerable effort, unless they take two-steps back in the meta-game and say "Ret... not for PvP".
ADDED: There are reports of Exorcism not working against specific NPC's (i.e. Chillmaw). This is probably a bug, but well worth checking against raid bosses over the next few days just to be sure that it doesn't extend past this one example.