Very interesting numbers, thank you for the effort (another couple multiverse instances laid waste for science). A few questions:
1) You mention that the showdown numbers don't include the GCS's themselves; did that phase feel right strength-wise (since you don't have to do distributed-defense at that point)?
2) The distributed-defense phase of the showdown threw about half a transceiver-response's force at you. Is it the overall weight that felt too high, or the spikes (specifically that first CPA) ?
It was interesting to compare the two - plus, I hadn't done game with absolutely no super weapons at all or at Diff 7 in a long time. I almost killed myself with some early recklessness. I think I may need to play some more basic games to get back into the habit of being careful.
1) For the post-Device part of the Showdown, the balance was fine in this game. I knew what was coming, so I played a very "forward" defense. I researched early what path the AI would take to my Homeworld, and then fortified heavily an adjacent-to-Core world on that path. Then I skipped a system, then captured and fortified another system on the path, etc. My idea was hit hard early, to give time to rebuild stuff later when the first blockade goes down, while using beachheaded Core turrets in every system on the path to whittle down the GCS. If the AI HWs had been closer, or if I had been unable to pre-determine the path, I could have been in trouble.
A Mil-III, 2 Fort Is, 2 Fort IIs, 1 Fort III, a full cap of HBC I-IVs, turrets Needler I-III, Laser I-III, and V for the other ranged turrets plus a bunch of mines was roughly enough to kill a GCS and its escorts. Actually, the GCS killed the Mil-III rendering the remaining Fort II and Fort III out of supply, so if I'd had an adjacent system to keep supply, all the stuff I listed would have been enough by itself.
2) On the other hand, a Mil-III, 2 Fort Is, 2 Fort 2s, and 1 Fort 3 + a full set of ranged Core Turrets plus mines and a chunk of my fleet was crushed by the first CPA. That was a huge spike, coming only 10 minutes into the Showdown. By comparison, the minute 20 CPA and the final CPA were laughable. Almost all the CPA was concentrated near one AI HW, which allowed it to overcome my blocker, but this also let me build a panic-nuke, cutting it by 90%. Thankfully, the AI stopped to destroy every last turret in each system it passed through, which gave me time.
I suppose it mostly came down to distance and access-control. I did a bunch of gate-raiding, and used that to prevent waves from going directly to the SD systems. I had also hacked or captured 6 of the 8 Core Turrets, and used that to build an additional buffer line of beachhead Core Turret/MiniFort sets on every AI world I had supply on, to keep AI numbers low, and both slow and attrition the CPAs. I still lost 2 systems to the CPA and another outlying isolated system to a Counterwave I couldn't defend against in time, but the HW and the SDs were easily kept safe, just because of the depth.
The Exos weren't a problem, because only one Exowave even had a Superweapon leader - a Mk I Siege Tower. Only in the final Exo did a single Dire Guardian finally make an appearance. Exos and waves also are suicide attacks - very few units ever retreat successfully, so there's little buildup to be concerned with. The only real threat in the distributed defense phase was the first CPA.
It would be another story entirely without the Core Turrets and MiniForts, however. Those are the heart-and-soul of distributed defense.
Overall, I was suprised at how easy the Showdown was. I had to pay more attention to what was going on than I did with the Transceiver, because I couldn't hide behind a single super chokepoint, but without the multipliers from superweapons, everything was managable.