With actions mandatory in the roles some jobs have most or all of their slots looked.
eg tanks MUST package rampart(no questions), convalescence (can be debated but most of the time you bring it) and provoke (again no questions) then you get 2 slots open 1 will go to shirk for tank swap and most of the time reprisal for more mitigation. meaning you cant package interrupts in raid unless you sacrifice 1 of the 2 really useful skills that are reprisal and shirk.
By increasing the number of Role actions from 5 to 6-7 chose would be possible in which skills you brings.