Just being a bit pedantic, I'm not sure if these are the exact categories, but it goes something like this:
Trash Mob, Ranged, Grunt, Elite, Brute, Giant.
Trash mobs are the four minis, ranged are anything with a ranged attack as a main attack (devilites included, greavers used to be here as well) as they usually do 10% less damage than Grunts, Grunts are the more common mobs, Elites tend to have a large variety of attacks like Thwackers and Mecha Knights, Brutes have hefty amounts of health like Alpha Wolvers and Lumbers, Giants spawn very rarely: Trojans and Dreadnaughts.
So, you're working on creating / gathering Ideas for new monster? I have a few ideas, so well, here they are. NB: A FEW.
~Gremlin~
Constructor-Elite- Has roughly the same amount of health as a same tier Gremlin Bomber. Can construct Constructs (Excluding Lumberer) of the same tier. Cool down for this ability would range somewhere between 45 seconds to a minute.
~Slimes~
Oozing Slime-Elite- Slow moving slime with a fast doge. Leaves a slime trail behind it that causes status effects. Is immune to all elemental effects. Comes in all Status Variants.
~Undead~
Necromancers-Elite- (I mean Really. Why hasn't this been done already OOO?) A variant of a zombie with roughly double the health of a same tier zombie. Has a devastating ranged attack similar to a Swarm Turrets (Very high normal damage), but with a status. They can teleport quickly after players, until it is within firing range. It generates a small aura, roughly half the size of a Deadnoughts, the instantly revives all zombies inside it every 10-20 seconds. These zombies will be the same status as the Necromancer that revived them. Comes in all Status Variants.
~Fiend~
Pit Boss CEO-boss/mini boss?- A high powered Fiend that throws large stacks of paperwork at knights, dealing heavy shadow damage and almost certainly Stun. This enemy would be able to convert all nearby Devilites into Overtimes, and Pit Bosses into Pit Slavers. Would appear only in Stygian Steeds, in the final arena, along with several Devilites and two or three pit boss
Pit Slaver-Elite- a more dangerous version of a pit boss, with the same amount of health, but with almost all the attacks of an overtimer. Highly deadly in Melee, they can / would inflict the status effect of the level. NB: Pit slavers DO NOT Turn Devilites into Overtimers. Pit slavers only appear during a battle with a Pit Boss CEO.