Fury warrior without any question.
for melee dps however its deeply depandant that your tank gets geared and know how to build threat.
It takes off when its bwl/aq geared.
Otherwise its rogue and hunter.
vanilla all the casters are so far off, and gets scaled away and warrior/rogue/hunter leaps further and further away the more gear you get, anyone argumenting against this dont know theorycrafting/scaling of vanilla.
Also best caster(if you will run a caster) is warlock, then mage.
shadowpriest was very underused so this i will not talk about at all.
Reason why hunter and rogue is so high is not only the scaling, its that they can go allout from the get go almost if they know what they are doing due to their threat reduces.
Warrior however dont have this, thats also why its hard for fury warrs to compete, becuse they deal most dmg and scales best, and rely heavily on the tanks doing their threat job very well.
And also some fights have "wing gush" or cant rmeember name wich redcues agro and makes it worse.
However these abilities start to disapear in aq/naxx wich is also the reason where this is where the fury warriors rise to the #1 dps spot.
If they would not had agro issues in bwl they would dominate even there.
Simple answer > Fury warrior > rogue > hunter > warlock dont go into speccs there becuse its diffrent dependant on how well geared you are and what content you are in.