because maybe the problem is not skill or ability related, but turnover. I had this problem in TBC that we were a small guild we finished Karazhan and starter Zul Aman suddenly 3 players dropped for various reason and we passed other 3 months equipping new three person in Karazhan.
All in all I do not care THAT much about gating if it is a matter of just completing that instance once as long as there's not a gear gating and I have chance to have our raid member to catch up if they remain behind for any reason without forcing my guild to rerun AGAIN previous instance.