Spec your tank Arms with 2 hander and grab initial aggro on packs by charging in, sweeping strikes, whirlwinding, and then stance dance back to protection with a sword and board weapon swap, shout, sunder ect. Your mages shouldnt be able to pull aggro and can aoe them all down right away. You'll find after stance dancing back to sword and board you are just as tanky as Arms, as you were spec'ed prot and the only difference is the first few seconds of locking down initial threat.
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