I have played a warrior in WoW for almost a year now, as fury. Yet I notice that my toughest oppenents are always in arms. I would like to know, why is it so hard to take down opponents of my tier who play in Arms? and what talents are used to deliver massive damage and healing reductions?
Right now arms seems to be the beefiest of the three specs (a year ago I'd have said prot). They have a decent ability to heal themselves through [Field Dressing] and [Second Wind]. If you combine that with Victory Rush which heals 30%(?) max health after a killing blow, they can be pretty tough to kill when they can kill really well.
Mortal Strike is the main ingredient that you're looking for here. It reduces the healing received for the victim and there are a few talent points you can spend so that it does more damage like [War Academy], [Wrecking Crew] & [Lambs to the Slaughter]. Plus it can be glyphed for another 10% dmg.
Another ability that really helps with dps is Overpower (does good dmg and happens a lot with [Taste for Blood]). Plus it can also be glyphed for another 10% dmg.
Those two, plus bladestorm, plus bleeds, plus debuffs which increase dmg taken... these guys are tough and when played well will make small work of decent toons.
Hope that helps!