Blizzard has been testing alternative versions of role queue in order to reduce the waiting time of those who prefer DPS position. However, the ride has been bumpy and Jeff Kaplan decided to explain why role queue with more than two DPS heroes is not coming soon.
It is no secret that the majority of Overwatch players prefers the DPS role to Tank or Support and that is one of the reasons why the 2-2-2 role queue format was instated. However, the role queue imposed new problems upon Blizzard, who found that DPS players' waiting time between games is too long.
As a result of that, the developers started testing 1-4-1, 1-3-2 and 2-3-1 role queue (Tank-DPS-Support) formats in an attempt to increase the demand for DPS and cut the waiting time for those players. However, this became problematic due to the nature of Tank and Support roles as well as certain heroes within them.
In the case of 1-3-2 formation, a single tank meant players had to pick a main tank like Reinhardt or Orisa and the off-tanks such as Zarya, Roadhog and D.Va lost their place in the game.
Meanwhile, 2-3-1 formation proved problematic because a single Support meant there were five people out to get them, making the environment oppressive for the players who prefer healers. Furthermore, as soon as the lone Support was down, the testing showed that team would crumble almost instantly.
Formation with just one Tank and one Support (1-4-1) took the worst of both aforementioned worlds so that one was no go as well.
According to Jeff Kaplan, Blizzard didn't stop there either. They tried moving off-tanks to DPS but this design direction meant further shrinking the Tank pool and the risk of removing certain players from the Tank role queue, who would otherwise jump in with D.Va or Zarya.
You can check out the full insights post on Blizzard's forums .