Blizzard actually did an experiment on this a while back, if I recall correctly, and also found that solo tank/heal sucked. Let me see if I can find the quote . . .
We actually tried a mode we called “411” because it limited comps to 1 tank, 1 healer and the rest DPS.
It was not fun and we didn’t enjoy it. The way the game is tuned, the importance it placed on the lone tank or lone support was too significant. Also, we’ve all evolved as players since 2016 and we’re much better these days at melting the tank or melting the healer than we used to be. Once your lone tank or healer died, it felt like you were forced to completely regroup with no chance of pull…