Playing Galactic war and my Sub-Commander no longer builds anything. It just stands there looking pretty. I started with an Orbital commander loadout. I picked up Advanced Vehicle tech. At this point, the sub commander would build a basic vehicle factory, but would never advance beyond it. I then picked up Complete Bot Tech, and dropped Advanced Vehicle tech. Every fight since my sub-commander just stands there, doing nothing at all.
Update: Just started a new Galactic War. Orbital Commander loadout. Basic Bot Tech is the only unit tech I've found. My sub commander will not build anything. It seems that Sub-Commanders won't do anything if bot tech is your only land unit tech. They will build naval if that is their only option due to placement.
Sure they do. Drop rate isn't the highest, but it's certainly still there. I have a game running right now with one.
They still drop on normal and hard, not sure about the difficulty levels above that. The biggest influence on whether you see one is probably map size; larger maps have more freebies at the start. Either way, it's easy to test. Just run 5 or so openings on an Uber-sized map and see if you get a subcommander in one of the empty systems. That's probably enough chances to be sure they aren't spawning for you.