Is damage type of bane property's 2d6 for weapons the same as base weapon (AKA slashing damage for longsword, ect)? Does this mean it is multiplied on critical hit?
1) Is damage type of bane property's 2d6 for weapons the same as base weapon (AKA slashing damage for longsword, ect)?
Yes.
2) Does this mean it is multiplied on critical hit?
No. It is extra dice from a magical source. Even though it does the same damage 'type' as the base weapon it is not considered to be 'base weapon damage'. It is identical to fire from flaming or cold from frost damage in how it handled and as such never multiplied on a critical hit.
1) Is damage type of bane property's 2d6 for weapons the same as base weapon (AKA slashing damage for longsword, ect)?
Yes.
2) Does this mean it is multiplied on critical hit?
No. It is extra dice from a magical source. Even though it does the same damage 'type' as the base weapon it is not considered to be 'base weapon damage'. It is identical to fire from flaming or cold from frost damage in how it handled and as such never multiplied on a critical hit.
But its still halved vs tiny swarms because its slashing, right?
Well, thats a bit suboptimal, but thanks for clarification!
Considering Bane is only a +1 enchantment it is actually pretty good. Don’t forget it also increases the enchantment bonus of the weapon by +2. So increases your chance to hit by +2 and adds on the average an additional +9 damage of which 2 is multiplied by a critical hit The additional enchantment bonus can often allow the weapon to bypass damage resistance as well. . Compared to the +1 to hit and damage if you simply increased the bonus of the weapon that is pretty good.
I have a +1 Longsword. It gives +1to hit and does 1d8+1 (~5.5) damage. On a crit it does 2d8+2 (~11) damage.
I have a +2 Longsword. It gives +2 to hit and does 1d8+2 (~6.5) damage. On a crit it does 2d8+4 (~13) damage.
I have a +1 Bane Longsword. It gives +3 to hit and does 1d8+3+2d6 (~14.5) damage. On a crit it does 2d8+6+2d6 (~22) damage. It costs the same as a +2 Longsword.
If there's an enemy you know you'll fight a lot (for example: Giants in the Giant-Slayer Adventure Path) then Bane is amazing.
Alternatively if you have a way of spontaneously adding Bane to a weapon then you can tailor the enemy type to suit the combat. This is rediculously powerful.
As a side note, Bane is one of the few enchantments that can give you an enhancement bonus higher than +5. If you have a +5 Bane Longsword then it acts as a +7 weapon when fighting it's designated foe (giving a +7 to hit and +7 to damage), as well as giving +2d6 bonus damage. Usually weapons can't get higher than a +5 enhancement bonus.