It depend a lot on fight duration and boss mechanic, which determine how much up time do you have. One of the biggest reason FM have such high damage isn't really because the class itself deal more damage for some weird reason, it's because they usually have the most up time out of any classes.

Also, some class have higher "advantage" than others when it come to DPS because of what they contribute to the party. For classes like Sin/KFM/WL with DPS buffs, their base damage have to be scaled down somewhat to account for those buffs, while other classes that doesn't bring any DPS buff don't have that scaling, so in a party those class get a higher damage difference, because they suddenly gain a DPS buff, while the other 3 classes already have their buffs as part of their rotation anyway.

Then Des/BD is different beast altogether because while their grab grant a shit ton of DPS for the other members, they themselves deal 0 DPS in those 6 seconds, so their sheet DPS will be a lot lower than what they actually contribute.

If we're talking about sheet DPS, I'd say FM, Sin, fire BM and may be SF are standing at the top. KFM/DES lie at the bottom.

If we're talking about effective damage contribution, I'd say KFM > WL > Sin = DES = BD > everyone else.