There is one time, and one time ONLY to use Army: When the tank says "Pop Army". If I want Army popped, I will tell the DK when I want it popped. Otherwise, when I suddenly lose aggro, I will have a heartattack and blow all my CD's trying to reestablish aggro before I realize what went wrong.

My main is a Pally Tank, I have tanked the first two bosses of ICC 10 with him, and I have just as much trouble with Army as druids and warriors do. I lose all aggro to them, and the majority of my mana regeneration comes from blocks/dodges/parries and incoming heals. Yes, I have Divine Plea up all of the time, but it is not nearly enough mana regeneration compared to what I use. I need to be attacked and be healed to keep mana up, and a paladin without mana is just some guy standing there in metal underwear.

Also, kudos to the Deathknight who will Deathgrip a loose mob off the healer. I totally agree with him (even when I was in Retribution Spec this was true) that DPS is expendable. Not that I want them to die, if I do my job right they will all live through the whole instance...but if I (or any other tank) messed up, and it kills a DPS, we are probably still ok. If it kills the healer, we are generally all dead. DPS die from time to time, that is why we have 3 in a 5-man. And this was true when I was a dps as well. More than once I have died saving a healer, and I have never regretted it. I never do, never have, never will. I don't really care how often I die, as long as the whole party or raid does not wipe. And it is pleasant and refreshing to see someone else with the same attitude.