It would be very easy to fix diversity in a fight, make it so you have to incap certain parts in order to win. Not this you can deal without and eat the dmg. Make it a 9999 dmg ability like a full map "Tornado" if you don't incap garuda's wings. This forces you to bring certain mele classes.

Then everyone can QQ "waaa I dont' have a MNK to incap the tail how is our group going to kill it"!!!!