I ended up figuring out that attack slimes are honestly strong only after i finished the game, they dont do 3nough damage for hell mode but since they can clone themselves theyre useful for crowded fights, slimetoss is also good
Also did you know that the lust ability on lamia is bugged and doesnt actually have a finite duration? She just turns immortal after you use it once, i like to use her as a more defensive attack imp against shielded enemies because her parry skill shreds enemy posture bars, the imp cant hit shielded oponents in comparison.
Other than that the attack harpy is a strong attacker because of high pitched note (which is bugged and has a bad tendency to miss but you can counter that with a second attack harpy using magical boom so it hits all enemies in the screen with all notes at the same time), her encore passive is also strong.
I think the support succubus is strong mainly because of the instructors passive that boosts SP bar by 10% for everyone and the cupid skill that turns the bat into a nuke, but i dont think the attack succubus is as worth it because shes too squishy and doesnt provide the same offense in such a wide area like other attacking units and she is already beaten by attack imp in raw damage too.
lastly the support dryad using the nurture skill (heals one ally and fully regens SP bar to them) is probably the best healer with supportive utility in the game imo, she can just fire it from off screen and you dont need to hover over her to fire. The strongest support combination i have found in this game is using the dryad with support succubus and for extra SP generation, with this combo allows you to spam skills more frequently which results in pretty strong teams.
TLDR: My strategy for this game ended up being maximizing as much energy generation for the characters to shoot their skills out as humanly possible, minimizing the number of different skills that require me to hover over a character to activate them and maximizing the stun potential of the team with attacks like poison swamp from support lamia, high pitched note and magical boom from attack harpy, mud storm from attack slime (and a small niche of cloning for especially crowded fights also for the slime), roots wrap from the defensive dryad and cupid from support succubus. I prefer offensive units with either wide area of effect attacks for crowd control or high endurance and high damage so they rampage from offscreen without me worrying about them, these two definitions make the slime and harpy strong crowd control options and the attack lamia(with lust) and attack imp(with devils incarnate) strong offensive units for their endurance and damage, i sadly dont consider the attack succubus all that strong because despite her strong damage she lacks endurance and wide AoE, which means she ends up dying offscreen more often than not.
Another strategy i've found was that combo grabs (like when an enemy is grabbed by both a harpy and a succubus for example) are pretty bad, i am unsure of how they work but they dont deal enough extra damage or have enough restrain time on one enemy to justify sacrificing the presence of another one of your units in the field since they cant fire skills or passives while grabbing people
Some of the teams i've made with the ideas above are
im kinda curious if anyone managed to find better teams than these by just spamming passives or if someone found a better SP generator with more efficiency or role condensation than support succubus and support dryad