Is it only based on SPD and HIT?
Do different weapons matter apart from their stat modifiers to HIT?
Does the opposing monster type matter regardless of base stats?
When will a character's attacks always miss another character? (Formula?)
Do the hit/dodge mechanics vary by game?
Primarily curious about Disgaea 2 in particular so I can min/max the opponent levels in the Red Waterfall zone for early powerleveling, but will give points for insight into dodge mechanics of other games in the series as well.
Best Answer
Speed and Hit are the primary factors, though facing has a minor effect on accuracy (I've never noticed exactly what %), and some Evilities affect accuracy (such as the Ninja having 50% base dodge change if attacked from the front and Mothman having a 50% dodge change for projectiles or something). Weapon types have no affect on accuracy beyond the basic HIT bonus/detriment they may or may not have.
As for a specific formula I'm afraid I don't know. I just know that generally your HIT should be within the ballpark of the target's SPD or you'll either be sure to hit or sure to miss. Stealing has a much higher HIT requirement than simply landing a skill, too.
Also, the games will generally display "99%" when they mean "100%" accuracy. I'm fairly confident 100% accuracy is actually possible, as I've played enough Disgaea I really should have seen 99% miss, and I haven't.
Best I can tell the hit/dodge stuff has been mostly the same per-game, though later games have more Evilities that can affect dodge rate (and before Disgaea 3 the games weren't always transparent about what special attributes, now called Evilities, classes had).