Pillowy Softness

Euripedes at Critical QQ has a post,Pillowy Softness, arguing that all those filling a DPS role should be putting out roughly the same amount of DPS in a raid. (Obviously this assumes roughly equal gear, skill, proper specs, etc.) His arguments make sense to me, especially given the direction that Blizzard seems to be going with Wrath. If all tanking classes are supposed to be able to tank any encounter and all healers are supposed to be able to heal any encounter, it only makes sense that all DPS should be able to DPS any encounter. I wonder how this would play out for places such as Naxx where we can expect to see a lot of frost resistant mobs?