The slime queen is aggressively breaking the system. 1-Every other turn she swallows someone, and 2-effectively gets two to three extra turns or so while that character is 3-rendered totally useless. 4-It can't be stopped by barrier apparently, and 5-she can freely spam royal guard which 6-gives the other slimes free experience on top of making it impossible to target anyone else. 7-All in addition to infinitely being able to instantly spawn a 8-buffed and full health replacement for defeated healers. 9-Also constantly spams an annoying dialogue box in the middle of the battle every single turn.
She can have only two. Maaaaybe three if she's not supposed to be the first boss. She's more of a pain in the ass with more total complicating factors than the scientist and dragon combined.
The rest oughta be distributed among the other enemies to spice them up I'd say.