I'm too tired to figure out the average exp you get for mastery with 2x mastery since It's 12:55 in the morning. I'll probably give someone a physical lightning if they can answer this tomorrow when I come back
After gaining a mastery level, the amount of xp required to get another level increases substantially. With 2x xp and 1 mastery, one kill would get you to ~135 mastery. The second kill to ~200, and so on. After 5-6 kills, I would say its 320-350 mastery. I might be wrong with the numbers, but its based off of a lot of experience.
