The gameplay environment in this game doesn't really support a DPS/Support via threat management like Thief did in 11.

-For one, the game plays just about a dozen times faster than 11. That isn't a knock on 11's part, they just play completely differently. While 11's slow, winding gameplay could be considered boring, it allowed the player to actively use many options to assess a problem. Go look at how many skills just one job gets in 11. Even after you sort out the strict upgrades, each job has about a dozen things they can do at any given time. In 14, gameplay is fast, immediately engaging, but more rigid. You just tank, DPS, or heal, and stay alive.
-Take in to consideration what a DPS has to do. Melee have to dodge the most while adhering to rotations to meet DPS checks. Asking a melee to additionally help manage threat with skills like Bully, SATA, Accomplice, and Conspirator while meeting checks is simply too much. Targeting allies means they aren't attacking and furthermore, what tank loses threat in a raid? Does ANYONE really want to put these kinds of skills in the hands of 14's PUGs and ask them to be responsible and skilled enough to use them in something like Titan EX? I sure don't. Call me pessimistic :/
-This brings up another point, in that 14 has no ways to directly screw things up. Sure, you can be awful at rotations and get hit by everything, but no skill in the game can actively wipe a raid (except perhaps Holmgang). With the mindset of the typical 14 player, this is a good thing; success is clearly defined.

People have to remember that FFXIV =/= FF11. Jobs like thief simply do not translate.