No, it isn't. Option 1 - cumulative score over the period of the games, easy. Option 2 - top 10% will change cause the nightfall changes daily. If you struggle to get there with a nightfall without much scoring, just wait till there is another with better scoring. Also, the scores reset at reset. Option 3 - just run one activity in a focus playlist 3 times, easy work. I recommend using a hunter cause there are more of them in the game and how it's set up, they will keep winning each time. Just cause you don't get something asap doesn't mean something is wrong, bungie didn't do something right, etc.