Yeah, I understand not wanting to go full mmo with all the details and stats, and for a 'porn game', I'm not really sure fine details fit with horny brain players. xD I think you want to keep it as simple as possible, but like you said, enough info to make informed decisions on what to use.
The adventure screen does give a relative expected level range for the enemy chain
zeraligator, but it does also ramp as you continue, and you have difficult and easy enemies mixed on some stages, so I agree to an extent of a visual. Honestly, threat visualization may not be as necessary if you know what you're up against. (Focus the hard hitters first, and you won't have to worry about a sudden crit that takes someone out.) You could do something like WoW with their elite dragon icons for leaders (silver) and bosses (gold), or show a heirarchy/specialization icon (magic attacker, physical attacker, tank/defense, and either minion or no icon for smaller threats). Usually, visuals also help in a game like this where a big sprite is the boss/specialized character, and little ones are minions if no hp details are shown. The other verbal way of doing it is like you said, with a lesser/major/element descriptor like a lot of Final Fantasy games.
I think the biggest pain point of this right now is the Gob Shaman, the Knight and.. the other one. It's tough to tell if it's better to down the shaman first since they hand out the buffs and do magic damage, or take out the minions since they can do a lot of physical damage especially once buffed. I feel like the shaman had more health, but maybe wasn't doing much damage, and the other two were supposed to be an armored attacker and a regular attacker; both of which were maybe a tad easier (unarmored more so) to kill, but really hurt if the shaman had time to buff them.
Elements/types do help too with knowing say a physical attack against a magic user (typically light armor) will be more effective, if I need to use an armor pen skill on an armored enemy, or say water against fire, umbral vs holy, etc. I know for now, most of the spells seem to be frost/water, but each partner seems to have an element type too. If I know Celica is water based, and we're up against lightning types, I may want to kill them quickly, play support to her since she'll be weak to their attacks, or just have her defend since her attacks may not do much anyway. If we're against fire types, maybe I focus more aoe so she can hit harder on what she wants (so a big spell isn't wasted on a 5% health enemy), or play support so she only attacks.
With all that said... this is mostly for those looking to min/max, or those with some prior knowledge using simple visuals and critical thinking to grasp the situation. I'm sure you're still going to get a bunch of people who will try to just spam the normal attack on everything and hope for the best. (Or grind to be high level enough to fast forward through all the fight parts that way.)