Ugh, ran into something quite similar to that on Eichenwalde tonight in a pug... Initially they used 6 Genji to attack (something I'll be hearing in my nightmares tonight), and then on defense they started with 5 Torbs and a Widow (swapping out to a 3/3 split of Torb/Widow).
Thankfully my incredibly skilled Mercy playtime of maybe an hour kept our Bastion playing "Count the bullets" with them enough for us to win. XD