The reason I brought it up this early because the boss is no pushover like Yata.
And Raid events never really scare me because even if you fail, you can always obtain help. Even easier if you're in a Union.
By "healer" you mean the self-healing Indra? She does have a cleanse yes.
I also saw a player who used Tyr and Gaia there and pretty much used her as a one time meat shield to ensure that no one else dies on the first burst before taking it down with Sieg and Tyr. But the problem is not everyone has Tyr or Gaia so....
Not sure if you forgot or just having Ama there for the one time sniper debuff. But she is going to be obliterated even if one tick of the rage burst hits her.
But don't worry, I had the exact same idea as you as well until I realised "Shet, I'm a fire main and the event is friggin water..."