define never? mid levels it's easy to out dps those... ret pallies in the mid levels are awesome dps.
outlands, it takes a bit more skill (mostly at researching where to get gear) to be able to dps well. I've out-dps'd each of those classes you say we will never out-dps.... only rogues really give me a run for my money. equally geared pre-raid level gear, my ret will keep up with and usually beat mages, locks and hunters, and often be neck and neck with rogues.
now, if by never you mean black temple... i don't know. it seems people say ret gear stops keeping us competitive at that point with those dps classes.
but for the other dps classes... yes, a correctly geared and played ret pally can out dps druids, shaman, priests, and most warriors.
but with dps that is possibly as good as those dpsers, will you be welcome in most raids... not really. when asked what CC i have, i only have the 6 second repentance and maybe i can OT if need be... not many people will even take 6 seconds of CC into account... cause it's pretty pointless. and OT'ing w/ dps gear can be dangerous in anything past regular instances (i.e. heroics and raids). and what interrupts do you have... again, none.. so if you can find a group that has plenty of CC and just needs someone to help them destroy mobs, you're golden :) if they still need cc or an interrupt they'll pass you right by. i'm stubborn and know that the right group will come along for me to be useful :) some people don't take rejection nearly so well though.
(here's where bodh comes in and says there's no way and we start our little debate in yet another thread... lol)