Load up the hollowed lair nightfall then you can farm lost sectors and public events around the area for progression(arc kills & fusion rifle kills). Then for the strike of choice (activities completions) load up the lake of shadows strike, you can use the graviton forfeit helmet with the nightstalker bottom three and run though to the end easy while invisible, the fastest time to do the strike on console is 3:10 with the invis hunters. So just keep farming that stike. Hope this helps Found by - LNG oreo, TwentyBeef