In this instance, blizzard is 100% to blame. As every single player who levels up to 60 find themselves lacking ilvl to que for heroic, even thou a good amount of them are more than capable of running heroic dungeons with the ilvl they get from levling.
And while a good amount of these ppl just manually run to heroics to do them outside of the groupfinder theres a large enough population that simply spamms normal dungeons to get the ilvl they need to do heroic dungs. These players have a skillset that is vastly above what the normal dungeons where tuned for wich leads to what the OP describes. Groups that blitz throu content that is undertuned for them.
Overall, its kinda sad the state of the game is at release, the only content availible is severly undertuend for a good portion of the playerbase. Wich leads to said portion of the playerbase doing the same thing they do in classic wow. Wich is creating difficulty on their own by attmepting to run the content as fast as humanly possible.
It would be such a blessing if blizz decided to open up m+ on day1, even with ilvl cap of what the m0 dungs are it would give players something to do.
Honestly, id go as far as saying the vast majority of "issues" in this game comes from blizzard forcing players of diffrent skill and goals together when its quite obvious that they don't get along at all.