LMAO.
I merely guess that popcorn 300aoe auras and boons were in general implemented to make the game feel more action based, so you pick up things as you roll through them, instead of targeting team mates to buff (like classic WoW had blessing of whatever in paladins)
But seriously, to balance the raids for ranged alike maybe i t wouldn't even take much effort, I suppose the following would do:
1. Make aggro toughtness based all the time, as that attribute makes sense for this.
2. Make aoe boons in raid have 2000+ range, but only for that game mode. The balance in other gamemodes seems to be more in check, so there seems to be no need to overhaul the entire combat system, just the combat system in the area in which it doesn't work like designed (as an example, in FFXIV you have different skills in PVP, that games combat system still feels.. slow and laggy, but they addressed imbalance by changing skillsets only in one game mode)
3. Make being in melee in general more dangerous. There need to be un-dodgable attacks that force an occasional move out of melee circle, that would promote the "switching of melee and ranged spec" fluency that I think the game was aiming at, or at least largely advertising such a gameplay in general.
Or: Remove sharing boons in Raids, as every class has high self sufficiency in general.. though this one maybe seems more extreme.
But on the topic of just in general class balance. I would rather have only 1 or 2 playstyles per class and have that be balanced, than 5 options of playstyle and sometimes even not having the class viable for endgame because all 5 are sub par. I don't think adding specs creates balance, it just changes current meta, and the idea of being able to play any playstyle as any class is appealing but it's really hard to pull off balance wise.
All that said, not being in general an active player in the past, I am not sure how often things get balanced, are the balance patches fairly regular? like every 3-4 months? How long has scourge been imbalanced?