It's not that hard to get. It's difficult to say this particular set, cuz I have over 1.500 hours in this game, but I got this particular set multiple times. So, my recomendation, use supergirl with drops for her and always do her plannet. Problably you will get 4 piece sets sooner than later. BTW, 1500 hours with divided attention in all characters, so if you focus one you should get everything for him way easier, besides the loot system being really bad.

how long did it take you to get this?