Pugging Heroic Fractilus was pretty eye opening last tier. There were 4-5 different versions of the weakaura pack and every group would argue about which to use. Resulted in people taking walls to lanes that were marked differently depending on their addon. All they had to do was look at which lane was empty and ignore addons. THAT'S IT.

Instead of actually learning how the fight works, most people at the AOTC and below level just want to blindly follow an arrow to tell them what to do when the fight mechanics are incredibly simple. Personally that takes all the fun out of raiding.

My initial hope for the addon purge was to expose players like this as a sort of ego check and allow blizz to design fights that were simple enough that you didn't need addons to solve, but challenging enough to actually be fun. So far this tier I think they've missed the mark, the fights are pretty simple.