That is fair. Although pelters are really funny when they go from a 90 degree shooting angle to direct fire.
A big hell no on this one. Catapults, Pelters, and Holkins are already over powered enough as it is. We don't need a long range rapid fire artillery piece.
I don't know about changed. Maybe, but maybe not. I vote for an anti catapult anti artillery unit and structure. Reasonings: https://forums.uberent.com/threads/planetary-invasions.54449/ Needed for planetary invasions and it helps counter pelters and catapults without being so unbalanced as shields.
Well I am all for nerfing static defenses. I still think a rapid fire artillery would be cool, but yes - the defenses you named are way over the top.