Overwatch 2

What heroes should we run?
McCree, Soldier: 76, Torbjörn, and Zenyatta.
I've seen alternate suggestions, such as Hanzo instead of Soldier: 76 and Ana instead of Zenyatta, but this is the safest/easiest comp. Also this guide will be mostly be written with the those 4 in mind.

Wave by Wave Strategy
This is a strategy from the Survivor achievement which involves surviving 4 bonus waves in expert. Therefore, you can be more lenient on compositions and strategies.
Also, Symmetra's rework changed the Summoner's moveset. The strategy that I present here may not be the best one to take care of her. If you have a better strategy, feel free to comment down below.

Wave 1 (x1 Reaper)

Wave 2 (x3 Shock Tires)

Wave 3 (x1 Junkenstein's Monster & x1 Shock-Tire)

Wave 4 (x1 Dr. Junkenstein & x1 Shock-Tire)

Wave 5 (x2 Reaper & x1 Shock-Tire)

Wave 6 (x1 Summoner & x3 Shock-Tire)

Wave 7 (x2 Junkenstein's Monster)

Wave 8 (x1 Witch, Junkenstein's Monster and Dr. Junkenstein)

Wave 9 (x3 Reaper & x1 Shock-Tire)

Wave 10 (x2 Summoner & x3 Shock-Tire)

Wave 11 (x2 Junkenstein's Monster & x1 Shock-Tire)

Wave 12 (x1 Witch, Junkenstein's Monster, Dr. Junkenstein & x2 Shock-Tire)

Bonus Wave 1 (x3 Reaper & x2 Shock-Tire)

Bonus Wave 2 (x2 Summoner & x5 Shock-Tire)

Bonus Wave 3 (x3 Junkenstein's Monster)

Bonus Wave 4 (x2 Witch, Junkenstein's Monster, and Dr. Junkenstein & x1 Shock-Tire)

Bonus Wave 5 (x1 Achievement)

Here's a video of me doing the run with randoms. We don't use the run described above since it's with randoms, but this should help give you an idea of how hectic it can get.

Here is a video of the described strategy. Note that this is last year, so the Summoner will be different, and that it's on expert, so your attempts should be easier.

Timer

Wave 1
-0:17 The Reaper
Wave 2
-0:44 Shock-Tire
-0:34 Shock Tire
-0:24 Shock-Tire
Wave 3
-0:41 Junkenstein's Monster
-0:39 Shock-Tire
Wave 4
-0:46 Dr. Junkenstein
-0:39 Shock-Tire
Wave 5
-0:49 The Reaper
-0:41 Shock-Tire
-0:32 The Reaper
Wave 6
-0:47 The Summoner
-0:42 Shock-Tire
-0:32 Shock-Tire
-0:23 Shock-Tire
Wave 7
-0:49 Junkenstein's Monster
-0:32 Junkenstein's Monster
Wave 8
-0:47 The Witch, Junkenstein's Monster and Dr. Junkenstein
Wave 9
-0:49 The Reaper
-0: 40 Shock-Tire
-0:38 The Reaper
-0:25 The Reaper
Wave 10
-0:55 The Summoner
-0:43 Shock-Tire
-0:35 The Summoner
-0:33 Shock-Tire
-0:23 Shock-Tire
Wave 11
-0:48 Junkenstein's Monster
-0:39 Shock-Tire
-0:31 Junkenstein's Monster
Wave 12
-0:54 The Witch, Junkenstein's Monster, Dr. Junkenstein
-0:39 Shock-Tire
-0:26 Shock-Tire
Bonus Wave 1
-0:45 The Reaper
-0:41 Shock-Tire
-0:35 The Reaper
-0:27 Shock-Tire
-0:26 The Reaper
Bonus Wave 2
-0:55 The Summoner
-0:43 Shock-Tire
-0:37 Shock-Tire
-0:35 The Summoner
-0:31 Shock-Tire
-0:24 Shock-Tire
-0:18 Shock-Tire
Bonus Wave 3
-0:48 Junkenstein's Monster
-0:36 Junkenstein's Monster
-0:26 Junkenstein's Monster
Bonus Wave 4
-0:55 The Witch, Junkenstein's Monster, and Dr. Junkenstein
-0:37 Shock-Tire
-0:35 The Witch, Junkenstein's Monster, and Dr. Junkenstein