Really? You think the solution is Silver Proving Grounds?...for premade groups would be an option to check a box requiring "Must have passed Silver Proving Grounds" because it's BS that players can queue for mythic pugs (not talking about friends on their own) if they can't even qualify for heroics.
As a 725 tank, I can solo most dungeons even on mythic difficulty and whatever the group does is just to expedite the run for added convenience. I don't mind carrying a competent player looking to shortcut his gearing process; the only thing that really gripes me is a truly incompetent player who keeps pulling extra adds because they can't aim their AoE, or the healer who's really dps playing an off-spec they've never invested time in learning (i.e., when I'm out-healing the healer 2-1 and they can't keep themselves or dps alive, even though I solo the boss, what good are they?).
I know I would use this option often, even if I had to choose between setting this requirement and setting an item level. What about the rest of you?