Well its definitly not unbeatable
we've been there for a month now, raiding 3 days per week 3/4 hours per day.
first week we couldnt get past the 2nd seed wave
2nd week we were getting to phase3 consistantly
3rd week we were getting to phase4 with 3 meteors and dead people
this week 70% of the attempts we got to phase4 with 2 meteors and everyone alive, got him to 30ish so its all about phase4 practice now
we got around 250 attempts in by now, the thing that really totally sucks about this fight is the length, 11 minutes to get a phase4 attempt, you can get around 15-20 attempts tops per raid (4 hours)