The bug appears to be related to Seal of Truth, as it's dealing over 60% of the affected ret paladins' damage, vastly dwarfing all other sources. The bug seems to be affecting PvP and PvE, as there are many reports of retribution paladins being nigh unstoppable in Battlegrounds tonight. One group of retribution paladins toppled Lord Rhyolith in under 15 seconds.
There has been no official word from Blizzard just yet on these developments, although we can be sure that there will be a change deployed to fix this bug as early as possible.
Reminder from the editors: Do keep in mind that abusing things like this is considered exploitation. Blizzard does have the right to ban you for abusing this if you're using it to bypass content à la our old friend Karatechop. Don't make Blizzard's job harder, and don't risk your account.
Update 10:00 a.m. EST Blizzard is aware of the problem and is looking for a way to solve it. They also issue the same warning we did -- don't exploit this.