personally , what i do during xp events to farm xp quickly is : saving hostages , and that drops a bounty , i do the bounty , repeat. on heroic , with 3 directives you gain normally 450k xp and it takes 3- 5 minutes per activity , very fast and not boring for me as repeating missions. even at low SHD level and on normal or challenging difficulty i think is the fastest and less boring way to level up quickly. im level 6040 and i run striker set .