I believe it has to end that those Warlocks spread their evil spirits and Fireballs across whole maps to monopolize nearly all monsters.
The best solution to fight this kind of thing is to let all magic circles and summons/placements disappear after a certain distance is between the caster and the instance/summon/magic circle[same right for all; noone should be able to place his skills and then run away just to collect the loot from the monsters killed by it later when passing by again]. This distance should be somewhere around 300 and 600 range (i.e. basically one to two screens away).
The idea is the following: If you summon/place something (e.g. an evil spirit, a Fireball, a Heal Tile, Merkabah chariots, a trap) and it doesn’t follow you around, it vanishes after the distance between you and it becomes greater than 300-600 cells. This would hinder people from spamming skills at spawn points to monopolize respawning monsters while running around the whole map, covering it with such instances.
Another thing that bugs me is that those “summons” create more threat than a player. A player should create more threat than a random summon unless he’s of a summoner class. Those classes could e.g. get an attribute that increases the threat produced by those summons (e.g. Warlocks evil spirits) while the Warlock, Necromancer or whatever summoning class is within a certain range around the summon.
Otherwise, monsters should priorize the players/pets/summons that actively attack and/or move around and not get drawn to inanimate, unmoving objects that look dangerous to begin with.
This way the botters/macroers/whatever and those monopolizing players would be forced to share the maps again with other players instead of making it ± impossible to grind on certain maps (demon prison district 2, dina bee farm e.g.).
If this continues, the new targets will be the Hunting Grounds that are to be introduced soon (if they are open dungeons like Demon Prison e.g.), making the game even more miserable for those who don’t like to play dirty.