I was farming 8-7 with the lineup in the picture.
Mist fired her special first that imposed 30% defense down on special skills onto the bosses and then the two ranger snipers fired their shots.
Seshat’s bypass triggered and her damage bypassed the SS defense down only resulting in 1175 much less than her normal over 1400 without bypass.
The description of bypass says bypasses defensive buffs so it is not incorrect if defense down is also considered defensive buff.
I wonder if this is intended as normally you don’t think bypass can be a disadvantage.