After experimenting with this perk for the first time, found one or two small bugs.
The daily fighter buff doesn't apply the +2 deflection AC on double weapons. That might be intended.
The +2 bonus AB on offhand doesn't stack with magic weapon. (Edit for clarification) Without magic weapon you get a +2 AB to off hand. With Magic weapon, you get +1 AB to off hand. (On sheet and on the combat rolls). I have yet to try to GMW.
(Edit2) Just checked. GMW and the bonus simply don't stack at all. It's as if your off-hand is always on GMW for AB.
The daily fighter buff doesn't apply the +2 deflection AC on double weapons. That might be intended.
The +2 bonus AB on offhand doesn't stack with magic weapon. (Edit for clarification) Without magic weapon you get a +2 AB to off hand. With Magic weapon, you get +1 AB to off hand. (On sheet and on the combat rolls). I have yet to try to GMW.
(Edit2) Just checked. GMW and the bonus simply don't stack at all. It's as if your off-hand is always on GMW for AB.