First of all people who complain about too many +15 are people who don't even try to gear up and sit on plat all day.
Secondly the only reason there are so many +15 atm is because of the quests giving stones and verdant making that event which granted some people over 30 stones and 150kk zenis.
If you were to farm outside of UD3 atm, your progression will be slow as hell. But since the increased rate per mob rarity will be removed, it'll be the same thing for everyone now, BUT with a ~30% lower drop rate. Unless someone finds an exploit there won't be many +15 anytime soon unless you buy kits for $$.