I'm in line to tank my first ICC 10 on Sunday. There are two Paladin's signed up to tank it, however, I'm being told that you can't have two Paladin tanks on Lady Deathwhisper because they won't be able to hold aggro against the casters.
Only fight i see that will be a problem to have 2 pallie tanks is Saurfang due to our hammer of righteous giving us snap aggro on the worms. Ghosts will target a random raid member and fly to them its their job to move tanks are there to taunt off each other.
I'm a paladin and tanked the right side in 25man pug tonight - it's the worst possible side for a paladin, but our other 2 tanks were also paladins so we had no choice. I had a lot of trouble at first until we had a DK deathgrip the far caster to me. I'd AS the near caster and tank by it, and taunt the melee, then Righteous Defense (second taunt) off the DK. You have around 10 seconds or so to build threat on them before they bubble and negate 98% of your threat. It isn't ideal, but it is workable. 10man should pose no problem at all, as the biggest problem is getting two casters within your AoE threat generators and each paladin can work a caster in 10man when it's the right side's turn for adds.
As for Saurfang, 2 paladins could tank it if at least one is spot-on with timers, never using Hammer of the Righteous with worms nearby, never using consecrate within 8 seconds of a worm spawn. The other paladin would then inherit his high threat when taunting. Otherwise, they may have threat trouble with exceptional dps in the raid.
Yes 2 pallies can do it but if you had a choice you would never send them both in. Hammer is our second highest threat move. Both would have to be spot on with times or else worms will buff saurfang's runic power. Ontop of that at 30% you can forget about hammer because the timers speed up. So far this is the most challenging fight for a heavy pallie tank raid in ICC it can be done but you need to have the tanks more aware of the worm timer than having any other tank as well as tricks/misdirect every time you can on the active tank. The way most raids go the path of least resistance is the one your RL will take.
My guild doesn't tank the casters. We just let the melee dps lock them down, making whether or not a paladin/DK can tank them irrelevant. Not only that, but it doesn't completely make the mobs immune to spell damage, just mostly so. If worse comes to worse, taunt still works. I've had to do that on the opposite mob type on my warrior several times when my physical damage no longer worked. I had no trouble maintaining aggro until the mob was dead.