Is progressive content or the community to blame for player skill gap?

[Zojha]

I've never played WoW, but if it requires reliance on such things to be successful in endgame, that speaks pretty poorly, either of the game design, or of the players.

I am preeetty sure a great many people are already using the trigger warnings for A11S optical sights, so you can react before you can see the balls.
Right now, it's not standard to use it because, well...it's technically forbidden! But the moment official AddOn support is granted, the floodgates are more or less open and in the end, content designers will design their encounters around these AddOns.