Might want to look into npc aggro in this room.
If comparing with osrs, the NPC's never aggro you UNLESS you either attack that specific npc, or if you try to cross the rope. (This means, if you attack one of the mages, only that one mager will retaliate, the rest of NPC's are dormant until each is attacked. When crossing the rope however, they will all attack you simultanously. On the other hand, if you've made all the npc's aggro the members of the team that are not crossing the rope, the person crossing will not take any hits, as the npc's are busy attacking other players. )
It's meant to be this way so that the team can control who tanks the hits, very essential when trying to complete fast raids. Also lets the team split the amount of damage between certain players. Some players might have fewer supplies left than others, so this is a pretty key feature.
No idea how similar you want this to be to osrs, but figured I'd point it out.