+15% is nowhere near enough weapon XP
If I am wrong about the actual numbers for the mastery levels that unlock attachments, my bad because you were vague in the patch notes.
New XP Curve, with a reduced XP requirement, about twice as fast in the early ranks and 15% faster in total.
You are not clear about where the "early ranks" end, so I will assume you mean 20
15% Just wont do the job. It takes for Double XP event for the progression to start feeling reasonable as it is right now before the patch. The 15% is about 6 -7 times less than the 100% of the double XP event, people not even feel that
"Twice as fast" should go all the way into until mastery 40 where the last attachment unlocks and all the other levels are just bragging rights
You are bleeding out players, do not make half hearted measures that will lose you the attention of all the players who quit because of this horrid attachment grind.