Its use is pretty limited but I use it in "oh ****" moments in PVE when there are too many mobs coming or in Kartia when the boss and the wave of mobs hit the players at the same time.
In PVP you can use it as a counter for enemy party doing BR.
You should not use it all, waste of MP. Except in mass PVP as said before.
Or may be in some antaras, etc. Never been there.
You will never need it in kartias (lol), and any other usual activities.