Lead Encounter Designer Ion Hazzikostas has been tweeting about visual clutter and the developers' response to it in Warlords of Draenor.
@szspagna Completely agree. This is a major priority for us, and something we discuss among the class team, with our FX artists, etc., often- Watcher (@WatcherDev) February 6, 2014
This should have several effects. Not only will it make life easier for melee, and for PvPers as a group, it will also reduce strain on players' systems. While it's remarkable that WoW still runs on older systems as well as it does, it is slowly getting harder and harder for less current machines to cope. And as upgrades like the new character models continue, it's only going to get worse. Things like reducing visual clutter, especially in raids, will be a huge help for system resources.