Tactician difficulty (the hardest) isn't too bad. I'm not sure what changes, but I haven't struggled much. You need to have decent builds and know what you're good at, but it's not hard.

One issue I have though is my character is a wizard and I normally control them. Ending up in a random ambush with them at the frontline is bad. I wish there was a way to customize your movement pattern and have your controlled character behind somewhere. I'm pen and paper, a good DM always asks how you're moving and in what order. I wish this did something similar, but let you choose who would talk or whatever else.