This is my first attempt in writing a "guide". As i'm not fluent in english, this is prolly not perfect, but well, let me know what you think about it.
I got the idea to talk about this because i heard complaints from guildmates when going in a "pick up" group.
So, what to do when you have to face multi targets.
First, i will talk about a semi multi tanking option : A warlock doing CC.
Helping a Succubus to stay alive:
Actually, a good warlock shouldn't be a problem, but well, reality is not exactly that way :)
What to do when a warlock will do Crowd control : let's say, you have a mage, and a warlock for CC. ignore mage's target, he/she will do his/her job with sheep.
Pull the warlock target, so you'll get initial aggro, this may save the succubus' life when seduce breaks,
and if you have time, also go on with a shield slam, and you're pretty sure each time charm will break, the target will go after you and not after the warlock's pet.
This should get you some warlocks as friend ;)
Now, the real subject, multi tanking.
i will call the mob to focus : Mob A, then the others, mob B, mob C, etc.
At first, I warn (well I warned as now we are used to play with each others), but be sure that it is clear for your group :
If there is more than 2 targets, they have to let you 3 seconds before going on dps like mad on mob A, unless you have a war "spe Fury" in your group (I will talk about that later).
The easy part : 2 mobs.
This should be pretty easy. Pull mob B, and start with a shield slam on it, then switch to your real target : Mob A, sunder, sunder, slam, then go on with your normal cycle.
Put on a Thunder Clap to be sure to keep mob B on you, and you're done. add a sunder or two on mob B at some point if you want to.
The fun part : 3 mobs
this may hurt a little bit, as mobs start to hit hard or pretty hard in heroic mode, depending on your stuff ;)
An important part in this will be kill order: for sure, target special mobs first if you lack of CC for them, i'm sure you know what sort of mobs i'm talking about if you've done some Mechanar for our beloved Sun Eater ;D.
Else, focus casters first, as they should go down faster.
Always keep "common mobs", or mobs with most HP for the end of the fight.
That said, let's go to the tanking part.
=> Pull mob C (this gives you a little bit more aggro with dmg dealt from pull), if there is a mob to be CC go to them and launch a Thunder Clap before your mage sheeps.
This done, your 3 targets will attack you, and you should get enough rage from their hits to do the following :
Shield Slam mob C, switch to mob B and Concussion Blow it, then switch to mob A, and do your Threat cycle.
Don't forget a demoralizing shout, this will add threat on the whole pack of mobs.
Drop some Thunder clap when it's up, and switch to mob B and C for a sunder armor every now and then. Just be sure not to switch to mob B and then to mob C during your cycle.
Else, you can be sure, you will loose aggro on mob A. Instead of this, 4 seconds before Shield Slam is up, sunder mob B, then go back to mob A for a Shield Slam, then target mob C and do your sunder armor.
** If you face mobs with weapons, you can add a disarm on mob B or C.
** If you're ahead DPSer, you can throw in a Shield Slan on mob B, so you're sure, he will not leave you.
** If you have a plate DPSer in your group, or a shaman well stuffed, you can let him focus mob A from start, instead of waiting for 3 seconds, as he should survive until you're done with Mobs B and C. This will let you get back aggro from him with one taunt and start with significant aggro.
Be sure to have thunder clap active all the time so they will hit less hard.
And disarm, concussion blow each time it's possible (Concussion Blow on a mobs not focused help to build aggro on them.
In addition to the aggro part, this will also reduce damage taken. Don't forget we are in Heroic :)
When Mob A dies, switch to mob B, and Concussion Blow it if it's stun. while it is stun, switch to mob C and Shield Slam it to keep aggro, then go back to mob B, and do your job :). If Concussion is not up, switch to Mob C first and hit the beautiful Shield Slam key, then focus mob B
Now that you get the idea, it's the same for 4 mobs, etc.
With 4 mobs, we have most of the time a caster, so actually, i get a shaman or druid (in dps stuff) to tank it and the group focus it to get it down really fast as i keep aggro from the 3 others.
If no casters, i deal with them all.
Well, that's not perfect, and there are propably other ways to keep aggro from several mobs, but this may help a little bit if you're confused.
Jezika, Uldaman, European Server.