If they are capable of tanking it and want to tank, they should have signed up as a tank, and unchecked DPS.

The person who is designated tank because he signed up as a tank is the one the healer expects to heal.

If someone isn't designated the tank, I assume they're not tanking.

They shouldn't try to while someone else is doing it already and it's working. That's just confusing , rude, and makes the instance more difficult.

...and no one cares that you can tank the non ICC 5 man.
What most people care about is a nice proper run where everyone plays the roll of their class properly.
If all of these mightier than thou, pull before the tank, non-tank tanks would just roll a tank and play a tank, LFG queues for everyone would be instant.

I actually healed a Ret-Tank earlier today. As in, he was specced Retribution, signed up to tank, but was also wearing tank gear besides his weapon.* It was an interesting run, since I had to heal more than I usually have to for that instance, but he knew what to do. Only wiped once, and that was because I accidentally fell off a cliff.

*His weapon was also the Bone Arbiter axe, which also made me feel good about his skills/gear level.

I'm tempted to try tanking with my Prot/ret spec (PVP spec) for shits and giggles.

If you see a Ret Paladin not wait at least 1.5 seconds before using Divine Storm (immediately after a pull) then they're not using the priority system right. Whilst it is true that Ret Paladins have no set rotation (FCFS) we DO have a priority system.

Judgement should always be the first attack used when a pull has been initiation (HoW only priorities over Judgement when the mob is below 20% HP). If somebody is using Divine Storm, even in an AoE situation, then they're DOING IT WRONG.

I know this is for tanks but I'll put this here for all you Ret Paladins to see. If you use Divine Storm as your first move when I'm tanking I will punt you out of the dungeon verbally.

HoW > Judgement > CS > DS > Consecrate > Exorcism > Holy Wrath > Divine Plea | basic rotation

Judgement > HoW > CS > DS > Consecrate > Exorcism > Holy Wrath > Divine Plea | 2pieces T9

Judgement > DS > HoW > CS > Consecrate > Exorcism > Holy Wrath > Divine Plea | 2pc T9 and 2pc T10

Judgement > DS > CS > HoW > Consecrate > Exorcism > Holy Wrath > Divine Plea | 4pieces T10

Now, if a DK uses AotD? I'll just freaken punt you. As a tank I AM a control freak. I HATE losing aggro, it's like having a freaken haemorrhage when you lose aggro on a boss then notice it's because of FREAKEN GHOULS.