We've got the (holy) power
One major difference between live and Mists is how much holy power we'll be swimming in. On live, our holy power generators (HPGs) are Crusader Strike, Hammer of the Righteous, and Grand Crusader procs. In Mists, our HPGs are Crusader Strike, Hammer of the Righteous, Grand Crusader procs, and additionally Judgment.
Not to mention that, thanks to Boundless Conviction, we can hold up to five charges of holy power at a time. Get your floaties!
Along with all this holy power, we're going to have some familiar, critical abilities that we'll want to be spending our resources on. First and foremost is our primary active mitigation ability, Shield of the Righteous, which we'll want to prioritize our holy power use on.
Invariably the most optimal plan of attack for spending holy power is to bank up five and then dump three using Shield of the Righteous. This will leave you two charges, which you can quickly pile a third on for an emergency Shield of the Righteous for a large melee attack you know is coming, or spend immediately on a Word of Glory if things are tight and you need that healing all pronto-like.
Banking will generally be the safest strategy, as always have two holy power sitting around will provide paladin tanks with all the foresighted cushioning of the ant, and none of the drawbacks of the grasshopper.
So, the priority as such can be assumed to be: Shield of the Righteous at five holy power (or an emergency), then Crusader Strike, then Judgment, then Grand Crusader procs, then some of our many, many fillers. For fillers we can't yet judge priority until we have final damage numbers, which are a bit of a ways off. On top of all that, there are ancillary concerns like keeping the Weakened Blows debuff via Hammer of the Righteous, and keeping Sacred Shield up on yourself.
Of course this is all before we even consider talents from the 75 tier: Holy Avenger, Sanctified Wrath, and Divine Purpose. With these in mind, I think it's fair to say that the rotation will be leaps and bounds more fluid and dynamic that it's ever been.
Indeed, Ghostcrawler seems a little concerned with how quick our holy power generation is, and the speed which we'll be able to make use of it. He noted that:
The challenge with the current SotR design is that Prot paladins generate Holy Power pretty quickly, which means any 3 Holy Power ability will be used often. We don't want SotR to have 100% coverage, or it starts to feel more like Inquisition or the Hammer of the Righteous debuff and not like a short cooldown. We could slow down Holy Power generation, but we're reluctant to do that, because it feels good coming in quickly and coming from abilities like Judgment.
And furthermore that he expects with this system that, "Paladins [could be] getting a 3 sec Shield of the Righteous about every 8 sec."
That said, I'm not super confident will see our holy power generation situation shuffled around a bit as beta continues.
Our stat values are shifting
If I were to tell you six months ago that haste will sort of be a survivability stat in Mists, you'd call me crazy, yes? Yet here we are, soon to be equipped with Sanctity of Battle, one only a retribution talent. Suddenly (and this is most assuredly long overdue!) we're going to get some survivability mileage out of haste rating.
Similarly, in the next expansion hit and expertise, long the dump stats of choice for most tanks in Cataclysm, will take on a new importance. In Cataclysm we didn't care about actually ever hitting the boss -- Vengeance did most of the legwork for us when it came to threat. Contrawise, in Mists, hitting the boss will absolutely be critical -- especially with our HPGs.
Crusader Strike and Judgment will only give us a charge of holy power if they connect. Shield of the Righteous will only actively mitigate if it "instantly slams" the boss. Grand Crusader procs, apparently, are the only HPG that doesn't have to actually hit to give its benefits.
The more our attacks and HPGs connect, the more often we can use our active mitigation and other holy power-dependent abilities and thus the more we can increase our survivability. And, thanks to haste, we'll be able to perform those abilities more often -- Bloodlust will finally do something for our survivability!
Theck ran a simulation of our stats with regards to block a month ago, and it was interesting to see haste and hit/expertise on the board like that. Both aren't end-all/be-all stats (it certainly does not look like we'll be stacking haste or anything), but they're not terrible, and they are no longer obvious dump stats. That alone is a very interesting change that will have huge implications for the next expansion.
The Light and How to Swing It shows paladin tanks how to take on the dark times brought by Cataclysm. Try out our four tips for upping your combat table coverage, find out how to increase threat without sacrificing survivability, and learn how to manage the latest version of Holy Shield.