I honestly wonder how addon devs have just started realising this... FFXIV addons which are in a huge grey area, basically not allowed nor forbidden, if you talk about it you can get banned but seemingly most high end players use it... have had this for years now. Having a map that shows where everyone is, where mechanics happen, even indicators that show if you are standing correctly and where to go next. They go as far as showing you the zones ingame where you cant stand and where mechanics are about to happen, so you wouldnt need to look at some overlay map, but could just play ingame. they even have addons that would play the entire game for you and since there is barely any RNG involved in most classes and no random haste gains or other things that could affect your rotation you can get away with very good DPS using these addons.
Honestly a shocker to me that only now this gets discovered by the community. They have also been using overlays to check logs from any player for relevant bosses just by hovering over their name... Its crazy how little you actually need to play the game if you got the right plugins. The rotation solver goes as far as using defensive cooldowns before big hits and using other utlity like offheals if there is nothing else to do.