So I currently have planned a very simple combat system with low numbers and simple formulas.
Physical Damage is calculated as (a.atk - b.def) for basic attacks. For physical skills, it is (a.atk + x - b.def), where x is the Power of the skill.
Magic Damage is (a.mat + x - b.mdf), where x is the Power of the spell.
Physical Hit Rate is calculated as (Agi + Luk + Base Hit). Base hit is almost exclusively defined by the weapon that is currently equipped, with small bonuses sometimes coming from class.
Magic hit rate is fixed depending on the spell. Magic Avoid plays no part in this.
Physical Avoid is calculated as (Agi *2 + Class Bonus), with class bonus being small bonuses of around 5-15% based on class.
Critical Rate for both types of damage is ((Agi + Luk) / 2), with bonuses sometimes being applied by either weapon or spell.
Crit Evade is (Luk). Occasionally this will be boosted by equipped weapon or class.
Both physical skills and spells cost HP to cast. Magic classes generally can not equip weapons, and when they can they do not provide bonuses to Mat. To balance this, most enemies will have significantly lower Mdf than Def.
Maximum character level is 60, with the player gaining the option to pick a class promotion once at level 20 and again at 40. Stats will generally end up somewhere in the 45-60 range at max level for third tier classes.
I'd like some feedback on this system. It seems good to me on paper, but I'm sure there's something I overlooked.
Also, when I got done with this I realized that MP didn't serve a purpose. I actually have no clue what to do with it. One option is to set it to zero and be done with it, but another option I though of was making MaxMP serve the function of Mat and making Mat another separate magic stat, and having different spell types scale differently between the two, but I don't know, I think that may just end up over-complicating things.
Anyway, I welcome any thoughts and opinions on the matter.