This is all my opinion, mind you, but it is informed from having lived through a game that saw many changes over a long period of time. I just felt like this needed to go somewhere, so take it as you will.
The reason dungeon finder and raid finder (the collective equivalent of our duty finder) was introduced was to get players into dungeons faster who weren't tanks or healers. However, in hindsight, it was a bad move because the reason the end game worked was due to the fact raid groups formed long before they ever hit raid level content. By working consistently with people on the same servers over a prolonged period of time, they run into people whose gaming habits, skill, and personalities fit together. Then that other player knows someone else he likes, and so on.
It was easier to form a productive community in the long run this way because you can still make it through lower level content with people of very different skill levels, and even if personalities clash, its not like they are bound by contractual obligation to stick with one another. As a result, a great deal of the social instability plaguing current end game was worked out on the way up instead of accumulating all in one spot.
This is why complaints of toxic players, requests to make raid content easier, and elitism are so prevalent following a month or so after release. It's a clash of personalities that used to be spread across the entire journey of the game.
But at the heart of the whole problem is the role disparity. If it wasn't for the tank/healer/DD imbalance, the concept of a cross-server dungeon finder would never have been introduced. So even if we removed the duty finder, the class disparity would need to be solved first. Party finder, on the other hand, does provide an easier way for people to meet from across the same server. I can't help, but think WoW would have been better off with that option than the way it went.