Well, I took a chance the other night and brought along 2 rogues on a PUG Shroud run I was running, and a couple more people who had rogue mixed in, and we had nowhere near enough DPS to finish. The portals were taking forever (can't sneak attack those), and we couldn't take down the 4 lieutenants fast enough, because we could not leave just 2 people on any of them, and 3 people on the self-healers wasn't cutting it.
Next run through, took barbarians and rangers in those characters' slots, and we had no problem whatsoever. Now, I'm going to be playing a ranger/rogue that I'm leveling, will eventually get to the Shroud and don't want to get denied because of the heavy rogue levels, but it is certainly difficult to run with too many who aren't completely optimized.