I just went into the Arena and clicked on the profile of someone a ranked a few higher than me, to see who they were using. They had Sara with them and were ~110% of my strength, so I thought why not give it a shot.
When I get there, they don't have Sara, they have the default team, which is of course stronger than one with Sara in it, since she costs an arm and a leg to upgrade once you get her and is always underlevelled.
I'm sure this isn't the first time this has happened; one particularly memorable time I saw a guy Arena ranked above me who only had like 25% of my power or something when I looked at his profile, and i was like what are you doing there? Challenge accepted. When I got to the fight he had a team that mopped the floor with me.
Is this just multiple cases of miraculous timing, where someone has updated their defender team in between my getting the list of challenges and clicking Challenge, or is there something else going on?
Cheers