From DJC:
First RM2K3 breaks it down between Weapon and Magic attribute types. The engine then picks the highest weapon and magic attributes of an object for calculation and disregards the rest. The two chosen percentages are then averaged. But if the object has a negative attribute (absorption) then it overrides all other attributes. This formula should probably be scriptable for users like me who don't want to ignore attributes or give equal weight to those chosen. I'd also like to be able to manually set priorities per attribute for the default formulas.
Weapons and attributes are a particular problem in Everlong. Each uses at least three attributes: Weapon based that enables skills requiring its type, Weapon based that determines damage multiplier, and Magic based determining its damage type (slashing, blunt, piercing). Then add all the other attributes that are elemental or effective against certain types of monsters, and attributes start getting overridden and disregarded frequently. I'd rather just make attributes that enable skills never alter percentages in calculation. Maybe they should be an entirely separate type of attribute. Perhaps you should allow the ability to create attribute groups and expand on the two defaults. Each additional group could contribute to the averaging process in the default formula, or instead require a script to even be considered in damage calculations.
Also it'd be fantastic if percentage modifiers could be directly entered onto objects instead of only relying on the A-B-C-D-E RPG Maker scheme. This functionality should be available both in the database and via spells, equipment, and battle scripting. Without this, the letter system forced me to do confusing workarounds to allow enemies to shut off their defense after a period of invulnerability, or to cycle vulnerabilities. The problem is skills cast on self or allies can only lower an attribute down in the letter system. Attributes can also only be lowered or increased by one letter value at a time, and only boosted or reduced to one setting below their normal level (before spells and equipment effects are considered). If these limitations, increases, and decreases could be set to a given percentage or letter on a per object basis that would make life much easier.
There's another problem with the reduction and boost system for attributes. Let's say I have an attack Thunder Slash that I want to deal damage and reduce the Bolt resistance of the enemy. The skill requires a sword (Weapon attribute), deals slashing damage (Magic attribute), and is thunder elemental (Magic attribute). Ignoring the conflict between slashing and thunder Magic attributes, if this skill lowers resistance it will do it for all three attributes, not just Bolt. This also causes problems with enemy attacks. To take into account a magic defense attribute for heroes, every enemy magic skill has a MagicDef attribute. The problem is skills that are intended to lower resistances but would be magical have to drop this MagicDef attribute, or else it too will be decreased. Example: spell Frost reduces Ice elemental defense, and should be magical, but must not be magical to prevent lowering of both attributes. But this also means MagicDef doesn't reduce damage from this spell. This has produced a number of questions from players who notice the inconsistency, but there's nothing I can do.
It'd also be nice to have a larger percentage range for attributes, and for any letter to go below 0% into the negatives.