It seems that the more content comes out the harder the battles get but one thing does not seem to change. The reccomended grade on the battles does not at all reflect what your facing.
An assault map with a grade of A++ has enemies with 2000 attack and defense and 1500 HP.
An regular road map grade A++ has enemies with 500 attack and 300 def nice and 400 HP.
The team grades should either be revised to actually reflect what you are facing or just removed. I am unsure what the procedure is for selecting a grade but it seems to very wildly from event to event and stages.