This could just be me, but I've been sitting around with my shiny new ifrit's blade just auto attacking for the last 10 minutes and never seen any additional numbers?

I've seen some minor damage difference per swing but I kind of just figured there was always a 5-10 variation in attacks in general. In the battle log I've not seen anything labelled as fire damage or additional on attack besides when i turned on sword oath.

Or is the bonus damage just added into the normal swing numbers and also happen to be that 5-10 damage rather than a sudden hit of 40 or something?