Ranger/Shaman Duo

[SenseiPikachu]

Friend and I are thinking of doing a shaman ranger duo, both of us are completely new so zero twinkage. Will the Ranger have difficulty tanking while leveling up?

Also, I've been reading in the forums that monk/rogue dps is higher than ranger. How much higher are we talking at lvl 60? Like will the they be putting out twice as much dps as a ranger or just 10% higher kinda thing (with comparable items of course)?

Thanks for any/all responses!