How do I break stalemates in Total Mayhem gamemode?

It is considerably easier to defend in the Total Mayhem gamemode than in normal gameplay: there are a lot of spammable defensive and movement abilities like shields (whose cooldowns even overlap) and jumps, it is very hard to confirm kills because enemies can often run away or defend endlessly, especially those like Winston, or D.Va.

This all leads to games often being stuck in "stalemates": endless overtimes, when neither team can push another away from the payload to end the overtime.

Even if you happen to kill 2 or 3 people with an ultimate ability, 3-4 more people still stay and defend. If another ability finishes them too, those 2-3 people you killed respawn already and are contesting the point again. And the cycle repeats endlessly until someone gets bored or makes a deadly mistake.

Particularly problematic characters are:

• Zarya with her endless bubbles, not as much for her (she will quickly die alone) as for her teammates.
• Winston with his spammable and tough sphere shield, plus awesome mobility.
• Orisa with her spammable shield.
• Mei with her spammable walls.
• Ana with her healing boost/denial via bionade and her endless sleep dart.
• Mercy with her ability to resurrect teammates, even if her ult is nerfed now.

How do I resolve such situations? What hero combinations are powerful against this?

Sombra.

Just be careful not to let zarya bubbles soak up EMP, and hope that your team is competent enough to wipe quickly after a successful EMP.

For this reason, it's best to pair up EMP with other 'area denial' ults to take advantage of the 6s helpless period of enemies. DVa bomb, Mei's blizzard, and Junkrat tire are a few examples. You can also knock back frozen enemies with winston ult, or grav them away from the payload. After a long enough stalemate, a single instant is all you need to secure victory.

There are of course more AoE denial ults like mccree and pharah, but they are not very useful in total mayhem apart from their ults.