Nice work! Some random design daydreams because this one inspires me:
I agree that Assess may be a little too "easy" of a choice, and I thought up a couple ways to address it that seemed fun. One is, if enemies with different visuals could only be proficient in *specific* areas (e.g. fire spirit can be proficient in attack or dodging, golem could be proficient in defense, mind, or some other third thing), I could see more texture in deciding whether to use it or not. An enemy who could only be strong in speed or defense would be easier and safer to sus out without checking. An enemy that could be strong in attack (among 2-3 other things) could be much more dangerous much more quickly, though. Meanwhile, there could be foes who could excel in attack or mind, but become *much* more dangerous with the latter than the former.
Just increasing the move's MP cost feels like a difficult balance - slightly too high and it would start to feel borderline worthless? But if you gave it another property, I could see it working? One thing I thought could be cool though would be like... all of the MP moves have an opportunity cost, in that using them results in you taking damage and not dealing any in return - if Assess also guaranteed the next attack would miss, this would remove that opportunity cost, which I think would enable you a lot more wiggle room to jack the MP cost *way* up, like as much as 5? Which I think could make it feel worth abstaining from sometimes without the move feeling worthless. Heck, depending on enemy design it could even function as a scuffed method of dodging dangerous attacks. Thinking some more, it would also more strongly differentiate the move from other means of collecting info, because a dodged hit would offer no information itself.
Anyway! This is just random musing. Thinking about RPG is fun.