I haven't done *every* yellow, but lots of them and lots of blue stars, whatever they are, the blue NCPD missions, and the assaults in progress. Those are great ways to get some seriously good loot including the occasional iconic or legendary. I'm still on meet Takemura and level 50 street cred, level 36. The side missions in this game are really fun. I think the overall stuff is less enticing to me than the stuff in GTA V or Witcher 3 but the side stuff is way more fun.LOL I am just getting to the "meet with Takamura" mission and I'm level 33 and I've done every side mission on the map. So any Yellow marker...
edit:
MINUS the buy a vehicle.