The covinent turrets need a major fix.Unlike the UNSC add-on upgrade.The covinent fully upgrade.So the UNSC get a relativly usfull main gun augmented with a powerfull add-on whilst the covinent get a worthless starting turret and upgrades that make them counter one type of unit and thats it.And then the add-ons are still more powerfull than the full counter of the covinent's.

Thats my oppinion.And no I dont use turrets they are usless as covinent.