I've run this dungeon countless times in test and probably at least ten since it hit live yesterday. As of this afternoon I've encountered a new problem that I'm assuming must be a glitch.
Me and my friends will kill the minions and then kill Sylster. Afer Sylster's death, though, the battle doesn't end. He in invisible, but his battle circle stay active and the fight goes another round, and it still shows his boss info with his health as 'defeated'. Being unsure what's going on but thinking we should keep fighting, we attack that round with whatever we happen to have up. Duting this time Sylster acts as though he is alive! Meaning if you hit dead sylster with an unbuffed attack, you will still be hit with Ra and can die - even though you've already defeated him!
If you make it through that round, sylster will come back to life for the round after that! And he'll he exactly as much health as you attacked him for during the round he was 'dead'?
After you kill him the SECOND time, he actually stays dead. I'm not sure what's triggered this, but WOW. As this didn't happen during test nor the first day in live I can only assume it's a major glitch rather than an intentional cheat.
As a follow up to this, in my final fight last night, Sylster did not come back from the dead - because he didn't die, lol. He had 3000 health left and was hit with a 4000 leviathan. He did the animation of flopping over/being defeated, and the immediately proceeded to take his turn normally in the battle (he was going second), with 1000 health left. He was killed again the following round and stayed dead.