I have been creating games with a 10 lvl difference and max 8 players.
I am level 89.
More than once, when my friend tried to join my game with a lvl 94 sorc, it told him “Character does not meet game requirements. You must be between level 99 and 99.” (He sent me a screenshot of the message, which I can provide if you need it.)
On one of these attempts when he told me this, I had several others in my game ranging from level 85 to 95. The other time he tried to join and got this same message, it was just me.
We have both completed the game in all difficulties with these characters.
Just providing as much detail as I could think of to help the devs figure this one out 