I have a ranger, I am by no means a "pro" at the class, but I feel I know my way around. In my normal groups on burns I am hitting like 475k peak dps, (first 30 ish seconds) by a minute I'm at like 335k. 3 ish minutes I drop to about 225k, can do 150k or so by about 6 minutes. (Ballpark figures, posting from phone at work, will have to look at parser more) but that's a ballpark. And 10-12 minutes I'm right around 105k or so. Is that at least a decent ballpark to be in or are other rangers completely stomping those numbers?
It'a going to vary based on what you are fighting and if you have a shaman in your group. Obviously headshots do a ton but I wouldn't factor that in to the equation.