What are the benefits of leveling as a tank?
Obviously, speed and efficiency are not two of them. Still, there a few benefits to leveling a slow, methodical juggernaut. For starters, the juggernaut thing -- you'll have little downtime from needing to heal or, ideally, run back to your corpse. You'll be able to take on mobs above your level, to a degree that some squishy DPS could not. I always enjoyed leveling as a tank in the past, because every time I hit one of those 2+ quests, I could easily solo it, without going through the trouble of finding a group to join me -- not that those exist anymore, but you get my point about being able to face down tougher mobs/situations as prot.
Moreover, the ability to flex those tanking muscles for a long period of time in a variety of situations can be helpful for hitting the ground running once you begin meaningful content at level cap. I haven't done much over the past few months other than one night of raiding a week, so I'm feeling a healthy dusting of rust that needs to be vigorously shaken off.
Especially if you've never tried tanking before and you plan to give it a shot in Mists, leveling (and the occasional dungeon on the way to 90) can provide valuable on-the-job training. Especially with regards to your rotation!
The talents you choose for leveling won't be very different from what you choose for group content. The emphasis, of course, is more on damage than anything else. As well as maximum up time, rather than increased performance in critical windows. As such, I recommend:
Level 15: Go for Pursuit of Justice, as the 15% base run speed bonus will keep you slightly fleet-footed while you're dashing around Pandaria on foot or mount, and sporadically giving you a staccato boost whenever you generate holy power.
Level 30: I think Fist of Justice will be the best choice here. I can't image you'll need to use crowd control much while leveling, but I might just be unimaginative. You can easily switch if an opportunity to "sap" something comes up.
Level 45: Sacred Shield, as always, is the best choice in this tier. You won't be using Flash of Light to self-heal, Word of Glory has that covered. Likewise, Eternal Flame isn't worth it, for similar reasons. Constantly reapplying SS will be good practice as well for level 90 content.
Level 60: Unbreakable Spirit is also the only real choice in this tier. Even though we'll seldom need cooldowns while leveling, I can see more value in shortening the waiting time between Divine Protections than I can between in being able to use Hands more often, for example. Basically, it will allow you to pull more aggressively.
Level 75: For pure damage, Sanctified Wrath is simmed out to be the best choice in this tier. You won't have to worry about survival as much, negating the need for Holy Avenger.
Level 90: When you hit the level cap, you're likely going to be hitting light group content, and won't need to immediately shift gears to a survival-dominated spec. As such, I recommend going with Execution Sentence, which is head and shoulders above the other two choices when it comes to DPS. That talent will serve you well for the 5mans grind.
Even though you're leveling as a tank, you're going to want to mitigate the slow pace by picking up quest rewards that enhance your DPS, as opposed to your avoidance. Especially considering the former also jives well with active mitigation, so you're really not hurting your survival chances at all with a DPS-focused loadout.
You'll want pieces that have the following stats first and foremost: strength, hit, expertise, and haste. Yes, even haste! Thanks to our Sanctity of Battle passive, haste has the wonderful effect of speeding up our holy power generation, and thus the uptime of our active mitigation. Not to mention the abilities that haste affects positively affects for us -- Crusader Strike, Judgment, Hammer of Wrath, and Shield of the Righteous (indirectly via increased HPG) -- are our heaviest hitters. So, just collect ret pieces, feel better about your leveling speed, and you'll even be able to use them in the random dungeons you might find yourself in without having to worrying about neutering your survivability.
If you have to do any gemming, use strength gems.
There's really nothing useful (in terms of actual gameplay) in the minors, so I'll stick to major glyphs. In particular, I recommend just going for two of our best damage glyphs and only one survivability glyph, since we we'll be needing far more of the former when leveling. Specifically those three are the Glyph of the Alabaster Shield, Glyph of Harsh Words, and Glyph of Divine Protection.
I did not include the Glyph of Focused Shield because losing the splash on fights with more than one target (which should be all of them if you're pulling mobs properly!) will negate the DPS benefit of the glyph. The other two damage ones, though, have no downside associated with them.
And you're off!
Okay, with all that said, good luck on Tuesday! If you are so crazy as to choose leveling as protection, then more power to you! You're fighting the good fight, a tradition that goes all the way back to the first prot paladins in Vanilla, who tied two cinderblocks to their ankles and marched into battle because, in the end, they wanted to see if they could do it. I know I'll be setting foot on Pandaria for the first time with a shield strapped to my arm, though I must confess I'm also bringing Dan Desmond to actually, y'know, kill things for me.
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.