Data:
War>Pld>Drk

Forum 'concensus':
War>>Pld>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Drk

War does most DPS. Pld a smidge behind war. Drk a smidge behind pld. Each by a couple % in damage.

Pld/War mitigation kits are solid and jockey for 1st based on how much a war is in tank stance. Drk is behind by X amount in mitigation (depending on how its measured. Its an inexact science) but still has enough mitigation to be effective in all content.

Group support: Pld by miles>War (shake it off)> Drk TBN. While nice, are not nearly as important as the volume on official forums suggests.

Drk is behind by a bit in every category that matters, but only by relatively small amounts. It's entirely usable. Just not optimal. But anything that is even a fraction of a % suboptimal is always slammed as 'useless', 'unplayable', 'broken' and 100 other hyperbolic terms.

There is truth to much of the forum complaints. But the extreme loudness exaggerates them on every count.