Blizzard forced this on HotS, Overwatch as well and this basically killed the games in many regions.
Simply because most of the time, non-dps are just not as fun and not wanted from the player base, yet Blizzard continues this design.
The games that flourished like Battleground style, requires teamwork but no one is forced to play a certain role by the system.
Everyone's able to perform the same roles, but people are given same set of capabilities within the game, and it's your choices that decide the roles. (I prefer to be a camper sniper, I rather be a scout for the team, I love collecting grenades and great at using them, etc)
Of course, we're comparing MMORPG and another genre, so if we consider other MMOs,
the system usually tends to be similar; making me think is it really the only way.
WoW relies on this almost outdated T + H + D system without almost 0 changes for over a decade and
a lot of players tend to avoid Tank roles due to pressure of being the leader in charge.
Ultimately though, had the dungeons and raids offer different design, this system wouldn't be required.
So I believe it's the game design that can be updated or tested in different ways.
What do you think?