The average rogue group is not necessarily very good (neither gear- nor skill-wise). Been hunting them solo as well and I've come out on top more often then not (although I do get stomped by some groups). And I'm not good at shooters nor have great gear (off the top of my head, 160K dps mp5, and maybe 80K health).
A lot of those guys just plain suck, and/or have shit gear. They get over confident when they see they're 3, 4, or 5 on 1. If you don't get greedy, don't panic and time your skills/heals/super right, some of those groups are a joke.
Well, some of them do know what they're doing, but a good spanking now and then is part of the fun.