The better solution to this is what most modern MMO's have started doing. Never have non-hybrid classes. Every job should be able to dps and fill at least one core position. But people still aren't going to queue as tanks and heals for pugs. They don't have to. If you are a tank or healer with even mid level skill by this point in the game you have an FC, 3-4 LSes for grouping and a friendslist full of people to group with. Yeah you might jump into a DF group sometimes. But why roll the dice when you can just form a group with people you know are good.