Expecting a fast run in anything but the current Expert Roulette is stupid. Even the 50/60 Roulette is also full of first-timers who are still leveling and won't necessarily have gear comparable to syncced people. A regular newbie will be going through all the 2.x Lv 50 dungeons in at most 110 gear, and 3.x Lv 60 dungeons in at most 240 gear, while vets will easily be wearing equivalent of full 130 and full 270.

Not to mention newbies will most likely have trouble trying to remember all those end-game dungeons in such as short span of time. We had months to get used to each dungeon and that leaves a strong impression. But people who are going through all the level 50 dungeons within a week? Most likely they're overwhelmed by all the guides and info by the time they get to 2.5 dungeons and have difficulty remember which is which.

Same for level 60 dungeons.

Hence it is stupid to expect fast runs in anything but the Expert Roulette, and kicking a DPS for something like, say, doing the same as a veteran tank geared to the teeth is just as stupid.