Though I haven't done a lot of Expert Dungeons, there's a lot of ground target circles appearing in other content. I park 4 characters at one end and charge in with my tank, turning around so the boss has its back against the 4 other characters and I have a good view of all characters. I do broadcast movement keystrokes to the 4 characters when they need to move. The tank stays put. Since they were parked on top of each other and facing the same direction, they move together.

Instead of moving left or right, I've started to prefer to move them forward instead. Then I back away with my tank (and the boss) to keep the distance. It feels more controlled, and it seems the 4 characters stays together and can avoid obstacles better.

The problem is when just one or two characters have to move, because they got a debuff or got pulled/pushed away somewhere. In those cases I simply switch to that character and move him manually. Since it doesn't matter which character I happen to be playing as "main", I can keep the fight going while I do so.

Sometimes when one character gets pulled/pushed I can still move the 4 characters as a whole, just moving everyone forward. Some characters will end up past the boss and some are still behind. Then I hit the "Follow" button which causes all 4 characters to turn around and face the tank, and thereby also face the boss properly. I can then either let them be spread out like this or move the tank away to gather up all 4 characters on side again. That's another reason I like to move my 4 characters forward - moving them forward will keep them under control instead of just spreading out more and more.