If you max out brave Hamedo will trigger 97% of the time, that's quite a margin of safety imho.

I set up the build so that the Black Mages would primarially do damage through draw out, which can't be stopped with innocent, or reflect. It would come down to if the Black Mages could wipe out the knights before they could break the reflect rings, but there would probly be like a 20% chance to break, if the knights were allowed into melee range.

Alternately the black mages could be equiped with Blade Grasp insted of Hamedo to block breaks too, however that can be countered by equiping Concentrate, so I didn't include it with the build.