What determines the difficulty level of the battle?

TransmuteJun

I understand that the map tier (Forest, Junkyard, Sanctuary) makes a difference. But within each tier, there is a wide variety of difficulty levels. In Sanctuary, I have seen between difficulty 27 and Difficulty 33. What decides the difficulty within that Sanctuary set? Is it the level of survivors from that 'opponent' player's roster? If so, does having level 33 difficulty on their maps mean that the opponent has 10 star survivors on their roster?

Firekid

We have a guild where most are level 70. Every battle is the same in sanctuary. Left section 27-28 middle 29-30 and right 32-33 to start with. Looks like 2-3 enemies are allocated each difficulty. I.e if you find the enemies with level 33 walkers first the the right hand section will be a lower level.