I'll add my 2 cents for what it's worth (probably not even a penny ):
I voted yes for a few reasons:
1) There are already story modes, but level ranges are missing (35, 40). These should be at least filled in if you have other level ranges. There should be no "locks" or "limits" unless you do the same thing for dungeon modes. This is one of the only ways to really gain relics in order to make/buy gear, as most dungeons aren't even being run anymore.
2) It's hard enough trying to get a group together for most dungeons. Since I have started watching chat for runs, I have run 1 To3 dungeon since I turned 34 - and that's with multiple requests about looking for the dungeon. When I log on, I queue for the dungeon, and I'm usually the only person in the queue. There is not enough dungeons being run to not put in story modes.
3) Sometimes it's better to know that not completing something is on me rather than on the group that I have. There are plenty of people on this game that don't know how to play their characters unfortunately, and that brings the "group" play down, part of the reason I hate grouping. Perfect example was back in the beginning of the game - Odhar Scar play with 90% of the people not understanding how to do the dungeon, even after explaining it to them.