Yep, that bug you hit is likely tied in with the rest of them. I watched all the tickets go by, even though I haven't filed them or addressed them yet. There's a lot of great ones in there to get to soon.
Keith has managed to absolutely slaughter the CPU usage during combat as far as the sim goes, which is fantastic. My instancing stuff really slaughtered the draw call count and thus the bottlenecks on the GPU bus and the CPU rendering thread.
Now there's a couple of main things left that are still major problems on my end. One is inefficient nesting of game objects, leading to expensive movement/rotation commands, and the other is over-reliance on renderers rather than direct instance calling, because that leads to massive waste on the CPU render thread for frustum culling.
At this point, in that slow battle savegame, if I send my fleet through to that planet and don't send the camera after it, the battle gets fought on my machine at 200fps with no noticeable hitches. Previously it was something very low and choppy with noticeable huge hitches even when I wasn't on that planet. All of this is Keith's handiwork in improving things.
If I go to the planet, there is now a very rough and hitchy 20-30fps performance going on there due to the rendering issues I've mentioned above. It's kind of ironic that the actual framerate hasn't gone up much at all after all these improvements, but then again I was getting sometimes multi-second spikes, and long periods of 5fps in that previous scenario.
I don't really know what to expect long term, once I get my things sorted out. But I have high hopes.