I don't have a problem with RNG calculations, it's the when and where. Removing the Hit/Parry/Dodge factor, you still have to calculate things with percentiles, and should.
Take resistances for example. Your stats and damage type should calculate a variable degree of damage, and their stats and resistances should modify that damage. You still have an RNG but you haven't removed the skill factor. It can still be dodged or negated.
So back to the OP, your weapons and spells should have a variable effect based on your stats. Not every character holding a hammer should be hitting for