Demon wall's attack pattern is Inside, Outside, Inside, Outside, Repel, For the entire fight. The hardest part is going to be remembering to keep the movement going when the adds spawn, honestly. Also DO NOT STAND RIGHT UP NEXT TO DEMON WALL, you can still hit him standing a little bit away and you will have less Repel shenanigans as being right up against him sometimes shoots you off in a random direction.

For the final boss, my group pulls him to the corner to the boss's left. Look at the floor tiles going from the statue to the wall, you want to stand on those floor tiles diagonally from the statue and they show you exactly where to stand. The rest of the fight is entirely on your party.