Currently the PvE end of things are played as a Tank a Healer and a Damage Dealer. You could argue PvP is more complex and more than just mere DD and Healing.
However, if you were in the dev team and it were decided to include a new role, especially for PvE, what do you think could have filled this spot?
Now, I do want to leave the support role out because mainly it's too broad.
Also;
A) It's the obvious go to option
B) We unofficially had it in the past like shadow priests of TBC
C) Jack of all master of none approaches don't cut it in today's competitive environment
D) I want to spark thoughts for more creative routes
This thread isn't about asking if a fourth role is needed. It most probably isn't needed at all.