It would be nice if there were two checks in place prior to queuing for content:
(1) Average ilvl necessary to join the instance
(2) Minimal ilvl weapon necessary to join the instance - doesn't have to be anything insanely high but should be high enough to prevent things like 2.X era weapons from being queued up with.
Not really a perfect solution as it's possible to change equipment after you enter but it's something. I have seem some pretty terrible dungeon clear times due to lack of good weapons in 4-man DFs.