You have the very mistaken impression that the fight is broken because it's designed for level 50 but you were there at level 60, and that's just not the issue here. Something that was meant to kill you didn't, and you clearly didn't know enough about the instance to even die right. That's a fault on you and not the design of the content. Sounds to me like you handled the add phase wrong and (very likely) the Sphere merged with the Egg, and you didn't know you had to be melee range to actually do damage, nor did you know the merged adds were designed to be buffed to near-invincibility - a punishment for failing the mechanic. Again, that's a fault of your not knowing and not the design of the content.

There's plenty of guides out there. I suggest reading up/watching before you go back in.