In my opinion.
Choosing the defense team is about thinking how the AI plays. You get the idea of good troops for the AI after playing a lot of PVP.
Another aspect in my thinking when creating a pvp team is the amount of luck needed to beat me. I tend to lose a pvp match only if the AI gets super lucky. So I build a defense team that NEEDS luck to work.
Thid point are the traits. Special third traits like the Sylvanimoras “entangle the first enemy” are great. To have the ultimum defense team, you need to look at least as much on the traits than the other values and abilities of the troops. And again think of them on how AI benefits of them.
After that pre-speach, my defense is:
The Great Maw
Since Mercy is fully loaded in the beginning of the match, it can create a barrier for Celestasia (if lucky). Celestasia can sometimes create some other color than it’s own (if lucky) to feed “the killers” Bone Dragon and Maw. Bone Dragon is THE troop for AI (if lucky), since it creates skulls randomly and (if lucky) can create a real harashoo. Also Bone dragons third trait comes in handy when Celestasia is down. The Maw was nerfed, but still it build’s up itself with skull matches, that Bone Dragon does (if lucky), and the ability to devour an opponent troop is super. I believe that in the later parts of the match Mercy is pretty weak, but at least it heals another troop and cleanses all. Also the mana colours are pretty well balanced in this team.
All in all I think that any loss to AI, no matter the team, is a weak performance by the player (that is you!). That’s because the AI is AI, and therefore a lot dumber than the player. The main aspect of winning with your defense is probably 5 star 10 level kingdoms. That is the most important thing in your defense team.
In my opinion.