Access to versatile ninjas early in the game is a huge advantage as midnight blade, kimimaro and sasuke can still be played later on the game and investing with these ninjas pays off and its free.. you can farm them everyday to get them to 5* especially with sasuke now with breakthrough you can bank on these ninjas while farming for your desired ninjas on treasure pulls.. while spending your coupons and resources to strengthen your battle power also it gives you great end game since the GNW treasure has been released you have more options to choose from since 7 mist swordsman benefits from most midnight blade buff has to offer not sure about elemental attribute but root and warriors killing intent / Life steal would work miraculously on your 7 mist team :D