But he's not poorly balanced because you're making him seem like an overpowered powerhouse, whereas he can be countered so easily, for a start he can't deflect Reinhardt, Winston, Mei, Zarya or Symmetra's weapons, so he's fucked against them, and anyone playing Bastion or McCree that goes turret or throws flashbang (Unless you throw it at the floor, that cancels his deflect and stuns him, but don't aim AT him) respectively BEFORE he's used deflect just deserves to die anyway... honestly he's really not as good as you seem to think, you just come across people that happen to be good with him, lol.
Also you've gotta' be pretty good and have great timing to deflect some of the ultimates... but there are plenty of people that can negate ultimates, it's basically just a shutdown.