EDIT: REJOICE, YOUNG MAN. YOUR DESIRED COMBAT SYSTEM HAS FINALLY BEEN GRANTED.
Hmm... Maybe ranking things with a letter by tens would work. I.E. E = less than 10, D = 10-19, C = 20-29, B = 30-39, A = 40-49, S = 50. Then, as a means of determining the stats required to use a certain level of gear, define it by two ranks - its defense against physical and its defense against magic. The physical stat determines the weight of the armor, and thus the endurance needed to use it. Armor with a B-Ranking would take at least 30 Endurance to use, for example. Then, armor could have a certain level of effectiveness based on its ranking vs. the ranking of the weapon/spell trying to pierce it, with the attack needing a certain level of power to even pierce the armor, but the armor only applying its effects so long as it's actually what's being hit. To give an example, Aoife's bits of metal armor would probably have on their own a base level of D-Rank against physical and magic - known as D/D - Rank - but would only apply their effects if somebody actually hit her breastplate, shoulder-guards, or things like that. Her gear would probably block any E-Ranked attacks completely, while a D-Rank physical or magic attack would probably have its damage halved. Against anything above that, all it would do is prevent critical hits from being inflicted. Although, armor's defensive capability could be raised by the use of defensive runes. As she is now, with a rune applied to her cuirass, her chestplate could perhaps guard D-rank physical attacks perfectly, although it would still be unable to reduce damage from C-Rank physical attacks, and would take halved damage from D-Rank magical attacks. This could be designated "D+/D rank armor." With a better defensive rune, it might halve C-Rank physical attacks, too, earning it C/D-Rank designation, or perhaps it might block D-Rank Magic attacks, earning it D+/D+ designation. Or, with an even better one, it might block C-rank physical attacks completely, I.E. C+/D+. However, based on its weight class and rarity, armor would probably reach a maximum level of effectiveness. Say... the most common armors can't be upgraded with runes, limiting their potential to its default level. Semi-rare armors can be upgraded, but by no more than one full rank in both categories - I.E. starting at C/D rank, upgrading to B/C rank. Rare armors, like the Dame Paladin's set, could be upgraded up to the maximum potential of their weight class. Light Armor would probably reach its maximum level at C+-Rank against physical, with Medium Armor reaching its maximum level at B+ Rank against physical, and Heavy Armor tapering out at A+ Rank against physical. Against magic, the order is reversed, with Heavy Armor coming in only at C+, Medium remaining B+, and Light armor maxing out at A+ against magic. On the other hand, there IS no S-Rank in armor, thus meaning that S-Class attacks CANNOT be stopped/reduced by armor alone. Each piece of equipment also could have a set number of rune slots that varies depending on the gear. The lighter the armor, the more rune slots it might usually have. Also, the larger the area of the garment is actually "armored," the more runes it will likely possess. To give an example, the Dame Paladin's Set is divided between Medium and Light armors. The Vambraces, Dress, and Circlet are all Light, while the Armored Corset, Faulds, and Arm Guards are Medium. As a result, the Arm Guards only have one slot, while the Faulds and Corset have two. The Dress and Vambraces each also have two, due to their limited surface area. Since the Circlet is entirely made of metal and consists only of light class armor due to its lack of protectiveness, it has a whopping five rune slots. Of course, anything save Active Runes or passive buffs to stats other than defense would have any notable effect there, given how tiny the Circlet is, so this method is something of a double-edged sword.
Now that I've concluded by rant on armor, allow me to explain my reasoning for simplifying the process down to a single letter ranking vs. letter ranking basis. That way, for enemy mobs, instead of coming up with detailed stats for all of them, we can just list their attack judging by letter ranking and still know whether or we could tank/block then. Of course, there's still the question of how we'll define attack and HP... For HP, maybe each level of VIT from 1-10 gives 10 HP, each level from 10-20 gives 30, each level from 20-30 gives 10 again, each level from 30-40 gives 40, and each level from 40-50 gives 50. SP and Energy would work the same way, with a basic attack draining 1 SP and special attack skills - powerful spells, multi-hit melee attack katas - each having their own built-in cost. For attack power, I guess that means we should probably define damage and weapon rank similarly. For an E-rank weapon or spell, its base damage should be somewhere around 1/5th of max E-Rank vitality, so that'd be 18 HP of damage. The principle would be the same for other ranks, too. Then we can add to that scaling based on your relevant stat - strength for melee damage or intelligence for magic damage. If your relevant stat is E rank, you get 1 point of damage for each stat point. For D, 2. For C, 2.5. For B, you get 3.5, for A, you get 4.5, and for S, you get a whopping 5 points of extra damage for each stat point you've invested, resulting in perfect-grade scaling of 250 extra damage. Finally, critical hits are triggered whenever you land a "perfect" hit, either striking your target dead on with magic or cutting/stabbing them such that their body provides no resistance, like a guy collapsing in half after a single katana swing in a samurai movie. If blocked even partially by armor, critical hits could not occur. Critical damage multipliers could be defined by where you hit, meanwhile. A limb would be 1.1x damage, stomach would be 1.3x damage, chest and vitals would be 1.5x damage, and throat/head would be 2x damage. These rules would be different against non-humanoid enemies, of course, but the principle is the same. In the case of mobs, We can just assume that their relevant scaling stats are the median value in their letter group they fall into. A B-Rank Mage mob, for example, could be assumed to have 35 INT and WIS. A D-Rank warrior mob could be assumed to have 15 STR and DEX. Their accuracy could thus be estimated accordingly.
EDIT: Ah, right, one more thing. Weapons are ALSO capable of being enhanced with runes to increase their level. Like armor, maximum weapon effectiveness could mostly be determined by size, sharpness, etc, with light weapons like knives, clubs, and fist-weapons capping out at B-rank, medium weapons like swords, axes, hammers, maces, spears and the like capping out at A-rank, and heavy weapons like two-handed greatswords, greathammers, poleaxes and the like capping out at S-rank. However, lighter weapons cause less encumbrance to carry, can be dual wielded, and attack much faster, while heavier weapons sacrifice speed and numbers for power and reach. Also, just because you have 50 strength doesn't mean you can wield an S-Rank heavy weapon. Rather, that would also require 50 endurance, which means S-Rank attacks, in practice, only belong to those who have either devoted a large portion of their total stat points specifically to doing just that, or those who have focused largely on INT and WIS instead.
EDIT 2: Aaaaaand it turns out I completely forgot about resistance based on stats. To keep matters simple, let's calculate resistance to damage by taking the same setup we use to calculate scaling for attacks, and then halving the output. So, your physical resistance would be 1/3 of your physical damage scaling, and your magic resistance would be 1/3 of your magic damage scaling. If your resistance is higher than the damage you're taking, it's negated.
I think that should just about cover our bases, as far as the combat system goes. Although, one other thing of note is that having enough endurance to use a set of armor/strength to use a given weapon doesn't mean you can use it without encumbrance. It means you can use it with the level of encumbrance a normal person would have, wearing/wielding that item. For swords and light armor, the two are functionally the same. For heavy plate mail and great hammers, though, to give a random example, it would still mean you were slow as hell. I aim to avoid the quandary of ninja-flipping giant-dads.
So, one final issue we need to address is what stats each class should start with. I, personally, think we should probably leave that up to those who are actually playing the classes in question, since it looks like each person is playing a different class from everybody else. That way, we can all hopefully min-max our builds as we'd like to have them with a little more efficiency. That being said, I propose we all limit ourselves to 75 starting stat points to distribute roughly according to our builds' focus stats, with the additional regulation that there must be at least 4 stats equal to or less than 5, and at most 3 stats above 10, with 15 being the highest possible amount of points you can start with in any given skill. I've come up with working beginning stats for a Longarms here to demonstrate what I mean.
- Level: 1
- HP: 100
- SP: 90
- Weapon Grade: E, Physical
- Armor Grade: D/D for Medium pieces, E/C for Light.
- P. ATK: 24
- M. ATK: N/A (No Magical Weapon equipped.)
- P. RES: 2
- M. RES: 1
- VIT: 10 (E)
- ENG: 9 (E)
- END: 10 (D)
- STR: 6 (E)
- DEX: 13 (D)
- INT: 4 (E)
- WIS: 2 (E)
- AFF: 5 (E)
- AGI: 15 (D)
- LCK: 1 (E)
And now that I am done once again assaulting your eyes with an unsightly wall of text, might I once again solicit your thoughts on the matter? XD