Unfortunately the system is such and we need to play by the rules.

In real pvp, you are able to stop the enemy's mystery with a combo acupuncture or immobile, but you can't with auto.

To counter this, you do not necessarily need to play your best lineup. Instead, you need to form lineups that are less reliant on mysteries hitting the right target because AI will always target lowest hp.

An example of this would be the water meta which is so dominant because it does huge aoe attacks on every round.

Another good example would be Roshi destroying a barrier in round 2 which effectively disables the enemy's damage output.