Looping teams aren’t good on defense, because the AI plays them poorly.
Gorgotha, while a really strong front tank, isn’t really good on defense either, as the AI will just spam his ability instead of using the rest of the team.
The most brutal defense I’ve run into lately has been Maw/Famine/Famine/Mercy.
Other good defenses would be anything that makes good use of Empowered troops… I’ve seen 3xScale Guard or 3xSiren besides the obvious Mercy.