That is exactly why Frazier is gone,
Like the offense, the defense needs to mix things up, neither side of the ball can do the same thing continuously and not get figured out, so you are correct in which the defense must be more aggressive at times, just as Dorsey and Josh need to mix in the short chain moving passes and run plays, you have to keep the opponents on the back foot as much as possible, gotta keep them guessing. From what I have read and watched, McDermott has already started implementing this during the first two days of training camp, it is why they fired Frazier and Sean took over play calling on the D side.