Somebody may have picked up on this before but its new to me!
Basically in Vol.2 at Lv.100 I can one-shot Vol.1 armored bosses like the Horned Archelon with a Surprise Attack for 8999 damage. However in Vol.3 at Lv.150 with even way better gear, instead of one-shotting it I instead do 899 damage and instead of the battle being instantly over its armor breaks off and it needs to be hit one more time (for full damage to) for it to go down. Its the same for Vol.2 armored regular & boss monsters. Regular ones will be defeated with the initial hit, but the damage won't be in the 8999 - 9999 range. Instead it's around 800 - 999.
I'm guessing Surprise Attacks ignored "armor" in Vol.2 (and maybe Vol.1 to?) but was changed in Vol.3 for some reason or another to not ignore it?