nvm I got the prevent faction infighting in - based on the area that you mentioned before in combat.qc/T_Damage 

I tried adding this , and different monsters in different factions do fight, but strangely only when they first took damage from the player

//>>> If no player found, look for monsters
if (!client)
{
//client = find(world, flags, FL_MONSTER);
client = find(world, classname, "monster_*");
while (client)
{
if (client != self && MonsterCheckEnemy(client))
{
r = range(client);
if (r != RANGE_FAR && visible(client) &&
(r == RANGE_NEAR || infront(client)))
{
break;
}
}
//client = find(client, flags, FL_MONSTER);
client = find(world, classname, "monster_*");
}
}