I think taking on 3-4 Trojans at once, no other enemies involved, would be a substantial challenge. We see Lumbers grouped like that all the time, why not the horses?
So why don't we ever see Trojan trios? Quartets?
In Firestorm Citadel, the final fight of depth 27 consists of multiple waves. The second-to-last wave has one trojan and many zombies. If I recall correctly, the last wave spawns as soon as you kill all of the zombies, even if the trojan isn't dead yet. And the last wave has two more trojans. So you can fight three at a time there.
Enemies are classified in 5 ways. Minis, Regulars, Heavies, Elites, and Minibosses.
Minis are found in compound, usually spawn in swarms.
Regulars are the regular enemies you fight most often. Gremlins, Spookats, Zombies, etc.
Heavies are things like Wolver Alphas, Lumbers, and Giant Lichen Colonies.
Elites are Gremin Demos, Mecha-Knights, and Greavers.
Trojans are minibosses.
In each level, enemies have a set spawn point that can be memorized if you learn all the layouts, but arenas are different.
In arenas, there are less common "general spawn points". For example, a spawn point can simply be a "turret" spawn point, accompanied by "Gremlin Thwacker" spawn points. For the general "turret" spawn point, it'll spawn the turret that is in the same family as the arena. But if it is, say, a fiend arena, it'll spawn the closest thing. For a fiend arena, this spawns a Howlitzer instead.
This was much too long a wall of text, but I think it gets the point across. No, you cannot fight 4 trojans at once.
In your face Fruitalicious!! :D
And you are not quite right with the monster categories.
Well, I was close enough.
Now fight 4 Tier 3 trojans at once.
Trojans and lichen colonies are their own class of monster. Lumbers and alpha wolvers are another tier of enemy. These enemies have a large health pool and a fair amount of attacks, making them a difficult enemy to fight, especially in higher numbers.
Pretty sure the game takes a "class" of monster, and then figures out what enemies go where in each level. In an "undead" level, a normal enemy spawn can spawn dust zombies and spookats, but as a secondary it can spawn devilites or gorgoes!
There simply aren't enough of the trojan/lichen colony tier of spawns in levels, as they're supposed to be a miniboss of sorts. While 3-4 trojans at once would be cool, the moment they all get out of sync when you're solo means a world of hurt.