It's funny that people complain more about one boss over another. Xavius was simple on Mythic difficulty (well under tuned.) To all of these guilds, however, he was a less important entity to kill than Kil'jaeden. People are more drawn to this raid boss, and they expected him to remain hard.
What cutting edge raiders don't understand is testing. They know their job, and they know it well: kill the boss. The tuning and testing happens internally, and it has to. That's the whole point to a QA team. Blizzard doesn't have these raiders on their QA team. Slootbag and several others have been o