I had a ranger up to level 28, heard all this hooplah about assassins, so I rolled one up. I loathed it - it's darn hard to tell what's going on when you have to be in the crush of the fight all the time, and tanks are too silly to position the mob for my attacks to hit. So, now I am betraying my assassin to be a ranger. (Dark Elf ranger 4tw)
With my ranger, I was killing groups of mobs like this:
Stealth
Pounce
Triple Shot
Snare
Zoom backward in a little circle shooting, doing CA's as they came up.
This was at level 28, mind, so it's doable even as a baby ranger. Mind you, always clear the little ghetto mobs first and have the bestest poisons/bow/ammo you can get. It isn't cheap but every group I've ever joined has been in awe of my dps, so you get what you pay for. The assassin does cost less, but goodness it's annoying in a group setting.