Tried SLKR vs SLKR and both team members were impossible to beat forever. See the attached image. Note that the defending team had new DC level 15 for Night vision Rey. Other counters did not work ...
Ideas
Keep your offence with you. I tried Bane and JMK prior to the mirror and they were destroyed in several seconds due to this DC, which could be acceptable. Then I used the mirror as the last hope, but it is bugged.
It's not bugged, you just didn't bother to read Rey's abilities correctly.
While in Grand Arenas: While Rey is untargetable from this ability, First Order allies can't be defeated.
I know her abilities. She should not be untargetable forever, only for one turn or so.
So with this DC it's a sort of infinite loop we had in the game before.
Unless you're 100% certain every member of your team had taken at least one turn, Rey can't be targeted and allies can't be defeated.
As I said, her Malevolent Lineage removes 100% TM from your team. She is using that to remove all your teams TM, WHICH IS MAKING SOMEONE ON YOUR TEAM NOT A TURN. Then if you use it, someone on their turn might not be getting a turn. See how that works?