I get the feeling this is the disconnect some people are missing. Certainly this does not apply to everyone in the discussion but certainly some who have chimed in.
A Mobile Arc is Not a Turret.
Turrets by rule as defined from 1.0 could shoot out of arc. Mobile Arcs are just that. An Arc that is not fixed that can change the direction in which a ship can shoot when moved around.
So one reason no one is talking about Luke (Gunner) on Miranda is she is a 2/3 primary weapon, on a medium base, where as the YT’s are 3/4 on a large base. So the Arc covers a massive area with a large base.
Also some people have not been accounting for the free action in a setup where actions are at an even bigger premium compared to what they were in 1.0.
I mentioned Earlier Luke vs Echo with Outmaneuver. Look at what happens if we give the Ship with Luke Outmaneuver. Luke’s ship maneuvers and either is not in Arc of the attacker or has use an action to avoid the opposing ships arc. Luke the at the beginning of the engagement rotates the Mobile Arc to face a ship he is not in Arc of. This turned the Mobile Arc ship into a more effective Wedge. Then it gets Magnified if the ship Luke is on doesn’t have to move the Arc because you can use the better of the modifiers based on your roll.
So again, in a vacuum or just by himself Luke isn’t earth shatteringly bad. Start pairing Luke with all the other upgrades and combinations and you start to see the abuse he could create.