The "social & explore" queue would end up empty. Simply because people tend to choose the path of least resistance and then cry on the forums if they don't like it. Either they lack the self-control too choose what they like (even if it's less effective) or don't like that others do the most effective route and feel forced to do it too... It's like with flying. Ground-crowd can stop using flying mounts anytime they want, but instead they make a fuzz and want to remove flying from all players. Just because they can't stop themselves from using flying mounts and hate the idea of running on ground when everyone else gets to their destination faster.
Or I could use the example of LFX and socializing. The option for not using LFX and for socializing are still there, but players don't use them, because other ways are faster and more effective. It's just the human nature...
The better way would be to make dungeons harder, to the level of Cata timewalking. This could be some good middle ground.