And now comes the Math...
Despite Paradox-related targeting quirks armor should be mathematically effective and I can prove that.
Here's coming a Warhammer, having 70% win ratio* over your Type-52. As bonus he's much less vulnerable to energy torpedoes and paired with corvettes really unstoppable.
*Test settings : 480 fleet size (120 cruisers) as my prefered size. Both fleets are done via cheats "research_technologies 1" and build on starport with Fleet Academy. Both fleets charge into each other from different sides of star system on Fast game speed (combat too going on Fast). 0 repeated tech, 0 admirals, 0 special resources.
There was 2 sets of 10 tries, in every set my cruisers able to achieve 7 victories and lose 3 times.
UPD. God damn it. Only now I'm found that my cruiser layout used T4 shield instead of T5... Well, let's call it "friendly advantage to shield users"
I'm using Advanced Ship Behaviour Modules mod, but it shouldn't have any influence as set to default Paradox settings. If you're really want I can reinstall pure vanilla game and re-run test with same settings.
UPD2. Done some more tests. While "Warhammer" losing to Type-42 battleships at fleets of equal fleet size (480), when I'm equal their fleet power by addition 10 more cruisers (120 warhammers had only 51.9K, compared to 60 Type-42 with 56.2K) - they begin to win over Type-42. Of course, warhammers unable to achieve victory against Type-41, but at least they're nearly to be hard counter to any cruiser or BB that based on anything except plasma cannons. I like it ^_^