Rogue is my vote. The simple fact is, for non-healing melee classes you have
Warrior
Death Knight
Rogue
Of these three, the first two wear plate, which is much higher mitigation than leather, and, all things considered, parry/dodge tend to even out, resulting in the poor rogue just taking more damage, which means more down time and more deaths.
Of course, you also have:
Paladin
Shaman
Druid
For your healing melee classes, and they tend to be very easy levelers.
As a note on mages, they suffer a similar stigma - priests are self healing, and warlocks have a tanking pet, so as far as clothies go, mages are the weakest - albeit with a permenant pet now from the frost tree, that may change (Albeit I would still give the nod to warlocks for life drain, harvest of souls, health stones and soul stones for survivability)
Warrior
Death Knight
Rogue
Of these three, the first two wear plate, which is much higher mitigation than leather, and, all things considered, parry/dodge tend to even out, resulting in the poor rogue just taking more damage, which means more down time and more deaths.
Of course, you also have:
Paladin
Shaman
Druid
For your healing melee classes, and they tend to be very easy levelers.
As a note on mages, they suffer a similar stigma - priests are self healing, and warlocks have a tanking pet, so as far as clothies go, mages are the weakest - albeit with a permenant pet now from the frost tree, that may change (Albeit I would still give the nod to warlocks for life drain, harvest of souls, health stones and soul stones for survivability)