Dice are not added unless specifically stated to do so.
Static numbers (like the +2 from bane) are multiplied.
Source?
Yeah, additional damage dice are almost never multiplied on a crit. The easiest way to think of extra damage dice is that they aren't ever multiplied unless they specifically say that they are.
Static damage is almost always multiplied. So, if you had a weapon that did 1 static fire damage, on a crit it would probably deal 2. Although it would depend on the ability. I'd can't think of anything like this anyways I can't provide an example.
Definitely no to both of those.
A critical hit means that you roll your damage more than once, with all your usual bonuses, and add the rolls together. Unless otherwise specified, the threat range for a critical hit on an attack roll is 20, and the multiplier is ×2.
Exception: Precision damage (such as from a rogue's sneak attack class feature) and additional damage dice from special weapon abilities (such as flaming) are not multiplied when you score a critical hit.
Precision damage does not multiply and damage dice from special weapon abilities do not multiply. Nothing about extra damage dice from other sources such as creature or class abilities, spells, feats, etc...
Is there a rule I'm missing that states these other sources of damage do not multiply on a crit?
Not explicitly, but it's an extension of the rule you quoted.
Not explicitly, but it's an extension of the rule you quoted.
Actually found the answer to my own question :)
Multiplying Damage: Sometimes you multiply damage by some factor, such as on a critical hit. Roll the damage (with all modifiers) multiple times and total the results.
Note: When you multiply damage more than once, each multiplier works off the original, unmultiplied damage. So if you are asked to double the damage twice, the end result is three times the normal damage.
Exception: Extra damage dice over and above a weapon's normal damage are never multiplied.
The reason behind crit hits are that you hit them in a vital spot or exceptionally hard. Since it is still just a single hit, your extra dice added still only count as one because they are not happening multiple times. The strength or bane or enhancement additions are all part of what a weapon does to the enemy physically so they are included in the increased calculations.
Only the enhancement bonus improvement part of bane is multiplied (the +2 it adds). The damage dice it adds are not. I just want to state this because your statement might otherwise confuse people.