Guns with legs and Atlas guns

So I’m a little concerned about the Guns with legs and the Atlas guns.
The ability to just drop a few legged guns and go behind cover while they do all the work seems a bit op.
What are your thoughts

It was a bit op at level 10, I doubt it will be at endgame.

Atlus takes some getting used to

Do the Atlas guns stay on target after reloading or do you need to mark the target for every magazine?