I'm not sure how you define competent. If you mean a group where all 25 people know what they are doing, I haven't seen one yet. If you mean a group where a few stupid people blow themselves up, but the group as a whole is able to progress through the entire raid without a single wipe, I get those all the time. Yes sometimes you get stuck in a bad group that seems to want to wipe endlessly, and those do tend to stick in my head more, but really most runs I do are pretty smooth.