High level pve content, basically all named that give feathers and a few other mobs, will have huge hp pools and act as if they are level 50 for spell resists, melee misses and melee damage taken as well as spell damage taken. Attacker count mechanic doesnt have any effect. Mobs no longer have puny amounts of hp and take 1 – 10 damage but have huge hp pools and take normal damage.
That would mean caster deal lots of damage, melees deal lots of damage and hence the HP of the mobs will be set accordingly.
We changed that to remove the attacker count mechanic and the trivialization via petspam. It also makes caster useful and makes group size affect the time required linearly (for example: every 200dps person you add reduce the time taken by 200dps). Petspam classes are still useful for raids as their pets will do reasonable damage to the mob, but our system will offer more and different options of killing a mob.