My issue is in regards to threat basically. A Paladin will obviously own me in AoE threat. I more or less /dance whenever we hit trash mobs because there's no point in even trying to do anything other than single target threat with a Paladin in the mix.
The fights where we have to transition threat seems to be a real problem with the threat tank (Paladin #1). His approach to tanking generates a lot of threat very quickly, so much so that if I don't solidly have the boss within a hit or two, it's his. There's nothing I can do to force RS to proc and it certainly won't proc when the target isn't even hitting me. My main strikes don't hit for nearly as much as the Paladin's do, so while I can taunt the mob back to me, it's like a very short wedding. I don't really have this issue with the other Paladin tank. He's not so much into numbers, thus he focuses more on just getting the job done and will happily stand there if need be to allow for adequate threat generation on my part.
So either something is wildly wrong with my gear or my spec or my rotation, or there really is no way for me to compete for threat with a Paladin in ICC. I know my threat revolves solely around RS and having threat to generate more threat. It's the hitting the boss when he's on the other tank part that is getting difficult. I don't feel I should have to use taunt just to return me to the top of the threat table. I should be right near the heels of the other tanks. What I see is them on my ass while I have the target, and me chasing their asses when they are on the target. Taunt seems more like a hail mary to the top of the threat meter and it shouldn't be that way... atleast not on a consistent basis.
Again, this really only became an apparent issue when the threat tank joined the guild. The problem may have always been there but the other tank just may have always waited for me to generate some threat before diving in.
Frustating as all hell as I outgear both of them and nothing that I do seems to alter the outcome.
The best way to solve transition problems on taunt-bosses is to speak with all other tanks and to make sure, that any tank, that gets a mob/boss taunted off, should stop using styles (or even autoattacks) for about 3 seconds. This is the easiest way for everybody to ensure that the taunting tank will keep the boss.
I run with a Blood DK in our 10 man runs and he does very well. Granted in ICC its a paladin's dream to tank. Holy Wrath insures agro on everything and with consecration on top of that other tanking classes don't have much of a chance on AOE trash. But that really isn't important as long as trash gets cleared. I know the DK I run with concentrates on trash mobs that need special positioning or attention.
As far as bosses go I usually drop just to auto attack for bosses where he is supposed to have agro. If your other tanks are arguing that when you are tanking they should be able to open up and do whatever they want and you should be able to hold agro over them, they aren't helping the raid out at all. If they really want to keep their tanking rotation going while you are tanking tell them to drop righteous fury while they do it... or Hand of Salv themselves.
The main importance is that you are holding agro over DPS. If you can do that then you can tank.
1) Make sure your threat generation is indeed as good as it can be. Seeing your own mistake is much harder than seeing others'
2) Make sure the overzealous paladin knows what "TEAMPLAY" stands for. If he's not supposed to rip aggro, he should not rip aggro, regardless of the reasons why.
As said, organize. If you know what's coming to the tanks, let all tanks know it.