Is... Reaper actually useful in the current meta? I know he's supposed to be anti-tank, but he has so little mobility that he can only ever ambush people (and if it's a tank, they're probably, A) not alone, and B) at the front of the group) which means he's just Bastion without the range.
Honestly, I've found Sombra better for taking down tanks than Reaper. Her new hack is pretty good against Roadhog--since even if he kills her, without his hook or heal he's gonna die to someone else. Same goes for hacking Zarya, Reinhardt, or D.va to get rid of their barriers (although it's harder to get a hack on them for a variety of reasons). And then she can ult and cause real damage with a bit of coordination.
And her usefulness stems from how agile she is. She can breach enemy lines better than any other hero thanks to her cloak, teleport, and medkit-hack.
Reaper is theoretically strong, but I can't actually think of the last game where he was Threat Number One.