I agree that 2-2-2 is often optimal when playing with strangers and there's little communication and coordination.
However it's not a magic bullet and goes to pieces pretty fast when 1) the tanks don't tank but over-extend constantly, 2) the 2 designated DPS persons aren't killing anything.
The latter problem is the one I encounter most often - bad Pharahs and Reapers are especially common, picking 1-on-1 battles away from the line of scrimmage (and not even winning those consistently.)
Of course, they'll always point to their medals when called out (well, duh, you have gold damage and elims because we're running 2-2-2; Lucio and Rein aren't going to out-DPS you, especially when they spend most of the match racing back to the frontline from spawn.)
Honestly, the lack of game sense even in the higher tiers is staggering. I wonder if Blizzard shouldn't do more to raise people's situational awareness (like, say, making the blue chevrons that denote team locations more informative.)