To be honest there seems to be a slight issue with her consistent healing in lower powered people.
Two people with around 1 million when fighting eachother, the attacker will always lose because the rounds are taking to long and all they have is a weak cianna to aim at maria.
She is a game changer for the newbies in comparison to when we were newbies.

I would advise to getting vipsanius agrippa to help with the maria issue. He can get to the back row together with cianna.
There is a tipping point where she becomes less consistent in healing the party and will heal 3 heroes average instead of all 5.
This would make it better.

Good luck