As far as I know the twitcher is the last of the enemies that the game will introduce. There are advanced forms of most of these, which are basically just higher level versions but I don't think there are any entirely new types.
That said, still not actually had neither of these new enemies hit any of my heroes so I haven't really had a chance to see how they actually work, nor have I seen my Alchemist's explosive armour do any damage because whenever it has gone off the nearby enemies have just died. Will try to keep things that way for as long as possible.
I also want to note that these nicknames are ridiculous, I mean "Cheese Arms", "Whats-her-name" and "Mr. Pancakes". These are definitely all nicknames sure, but not exactly nicknames forged in the heat of combat, they feel very jarring to me given that they are all bestowed just after one of the cadence is taken down.