Code: Old mastery: 10% Total Damage: 110 New Mastery: 15% Total Damage: 115 Damage Gain: about 4.5%

Code: Old Mastery: 110% Total Damage: 210 New Mastery: 115% Total Damage: 215 Damage Gain: 2.3%

As you get more mastery, the actual effectiveness of mastery goes down. Take for example a 5% mastery gain at 10% mastery on a spell that deals 100 damage:We then look at the same damage change going from 120% mastery to 125% mastery:All of this is because mastery applies to the base value of the dot, and 1% isn't always 1%. If you were to look at an (approximately) equal crit gain of ~1.5%, that starts to pull ahead of 2.3%.Other issues involve item stat budgets and how items gain stats going up in itemlevel. The same item going from 850 to 880 will only gain about 100 secondary stats, but will gain about 400+ intellect. This means there is also a (relative) soft cap as to how many secondary stats we can accumulate in legion