I've done basically this before as a hail mary play.
Comp game as we were against a 6 stack of a smurfing Genji (which he admitted in match chat) and his great, but not quite his level, team designed to support him. Pocket Mercy, Lucio, McCree (protecting him with stuns), Pharah, and Hanzo. This Genji had a card for 78% kill participation at the end.
First round, defense, Hollywood. We got rolled, hard. Second round, us on attack. For the first minute we were getting stomped. Then we talked it over (a PUG communicating, at that) and we went for the desperation play. Me on Mercy, Lucio, and 4 tanks. Rein, Orisa, Roadhog, and Winston.
We ran in with tons of health and tons of healing and captured the first point in one shot. We kept pushing with this funky group and pushed to the checkpoint at the big doors. Unfortunately they switched their comp up and were able to hold us there until we were off the point long enough for the overtime gauge to drop.
Not too bad. We went from getting pummeled to pushing forward with a tank heavy group against smurfs.