Nice idea although I have a suggestion that may make the minigame more challenging.
Basically make it so players must bring all 3 attack styles (range, magic, melee).
Ahrims has a 90% damage reduction if the player is using Range/Melee (Player must use magic against ahrims).
Karils has a 90% damage reduction if the player is using Magic/Melee (Player must use range against karils).
Dharoks/Verac/Torag/Guthan have a 90% damage reduction if the player is using Magic/Range (Player must use melee against these brothers)
If you want to display the prayers above said barrows brothers heads I believe it's something like:
Code:
case ####:
entityDef.anInt75 = 0; //0 = Melee protection prayer headicon
break;
Anyways that's my addition to your idea good job none the less