Yes.

You'll drink more between pulls, and have less ability to recover from double pulls due to lack of efficiency.

You don't even need a shadow priest. I first solo-healed normal Shadow Labyrinth as protection at level 69 with about 800 +healing, and nobody's ever confused me with God's gift to healers. Tank was level 70 but also in blues (and stood in Murmur's sonic boom...).

Expect to use a potion or two, though.

While uncrusheable is not a nescessity for murlocs, it's very nice due to blocking more of the attacks, as their hits are so weak that each block is a significant damage reduction. Of course if you're a few % short it's probably not going to be anything major as you'll just lose holy shield slightly slower on average and waste slightly more redoubt procs (due to them not running out fast enough before reapplying themselves and you take hits in the meanwhile).

To be fair though, you can't assume 100% uptime in AoE situations on Redoubt+Holy Shield, so your comment essentially is "Get more avoidance gear because that'll help you take less damage." Uncrushable really has nothing to do with that though, unless you get to be passively uncrushable, which requires slightly better gear than most people at TW.

Deignate the warlocks as yours to heal. Get the Kara Libram and put BoL on them. Fel Armor with a boosted FoL makes up fors whatever gear your wearing pretty easily. Just make sure the other healers leave your warlocks alone and that the warlocks hurt themselves with lifetap AFTER earthquake. Otherwise they can kill themselves if they aren't paying attention.

You won't have 100% uptime, but you'll block more as uncrushable than crushable. You can say it's because of your higher avoidance, but it doesn't matter. Also block rating is actually useful on both AOE tanking (as a blocked attack does very little dmg there, of course this varies depending on what you tank) and is also helpful for getting uncrusheable.
You're right though, that at the end the general avoidance+block rating for the downtime of holy shield/redoubt and pure avoidance for when it's up (if you're already uncrushable as during those times additional block rating does nothing) is what really matters, and large amounts of avoidance are probably preferable to uncrushability. Of course, block rating is also much easier to get due to rating conversions and item budget. So at the end while it's not the direct reason, being uncrusheable will mostly be better than not on aoe tanking.

Then run with just Imp RF and you'll be just above the threat of a salved non-paladin healer. (0.45 vs 0.35). If your threat control needs to be finer than that, you should probably just rethink how you're doing the pull.

The rule of thumb is +2 spelldamage ~= +1 TPS, so 143 spelldamage is roughly a 70 TPS boost. Windfury is roughly 20% more melee and SoR threat, so your total melee + SoR threat needs to be around 350 TPS to break even. If I were to hazard a guess, I'd say WoA+oil is better at lower gear levels, but WF overtakes it by T5 or so.

Of course, if you're using SoV, WoA+oil will probably always be better.

Regular Shattered Halls. (Which means it also drops on heroic, of course.)

A more practical use is farming the Demon Hunter Initiates on top of the Temple of Karabor in SMV. You can pull the entire field of 2-3 dozen initiates and AoE them down using the figurine as your only heal.

Pepe's is better for everything but trashpulls with a huge number of adds to tank.

Yeah, Pepe's is a lot better than Devilshark Cape; Devilshark does have slightly better avoidance (0.36% more; or 0.68% more contribution to uncrittability), but is otherwise largely inferior.

If you do need the defense or the extra avoidance over Pepe's you'd be better off saving up some badges for [Slikk's Cloak of Placation] (The bonus armor on it will probably also largely cover for the 22 block value); or you could of course hope to get the [Phoenix-Wing Cloak] off Al'ar, but I figure that if you get Pepe's thrown at you with no one else needing it you'll probably not be running TK any more.

The trinket is also just good for any soloing you might choose to do which pulls a whole load of mobs. It's also just plain one of the best passive avoidance trinkets if you're killing stuff which can't hit hard enough to get through your block value.

I've found the OP and the rest of the thread very useful for gear selection and tanking tips - many thanks. One small quibble with the encounters list:

EoD obviously requires a warrior, but after our first messy kill, we've had rather more success with a paladin tank for EoA. Soul scream actually seems a lot less dangerous for mana users with a small mana pool, and after the first (which hits for about 7k total), they all look more or less like this:

The second part is the mana burn damage. I don't think any were over 4k total, while they were often hitting our warrior for 11k, with the potential for 8k+ crushings and aura ticks. I've never been crushed by EoA, and although I guess it's possible if HS expires just after a soul scream with slow healing, it's fairly unlikely. Together this makes the potential burst much, much lower and so it's considerably easier to heal - I don't think I dropped much under 50% hp on last night's kill. We also found threat was less of an issue (although obviously there's no option of taunt/mocking blow/commanding shout chains at the end of the fight) due to the damage scaling. Avenging wrath+icon of the silver crescent at a decent damage multiplier provides a lot of threat.

Actually I'd argue (pretty heavily) that pallies are the strongest tank for RoS P3, especially if you use the seethe trick.

The ability to frontload aggro is a paladin staple, even if attempting to use the shield toss could well turn you into more of a punching bag than an effective tank, activating Seethe (other tank taunts and you spam yours to yank it off, while all DPS sits in the corner for 10 seconds), gaining the 300% aggro modifier, and tripping AW is simply unreal. Bribe a hunter to MD durring that period and it's just not realistic that you will be caught.

The ability to burn mana like it's going out of style, by spamming Righteous Fury if nothing else, doesn't hurt either. And don't forget you can hit him with Exorcism.

Though we've only downed him the once, so I can hardly pretend I'm an expert, I think that the paladin mechanics lend themselves a bit more.

Out of curiousity, how do you handle P1 with a threat trinket? Admittedly I still have the T4 helm (do. not. ask.), but I was getting hit pretty regularly, and could not tank him for more than maybe 5-6 fixates, and that's with 2 avoidance trinkets. We really didn't want to use more than 3 'tank' suited people (one of the primary tanks has full S2/heavy S3, so just wore that with a shield for the stamina), but we found ourselves having to ask a pally to step up for a fixate or two before he went down, and it's not like we often reached the third enrage. I'm very surprised to hear that you can afford the trinket slot for Icon.