There's a line from one of the stormtroopers that I didn't quite catch, but somebody told me he was saying the K2 series was marked as obsolete, as an explanation for why they don't show up.
I actually didn't notice CG Tarkin either, and in general thought the CG was really good, unless they were using more practical effects than I thought. My biggest complaints are that the argument at the shuttle relay doesn't make sense, and the stupid, pointless aperture door that shouldn't even exist.
I don't like Jyn yelling at the guy for "Just following orders" right after he says he specifically didn't follow his orders.
K2 was definitely the best, but I really liked the pilot too. As near as I can tell, he betrayed the Empire just because it was the right thing to do, and constantly got screwed over for it. Maybe they'd trust him more if the Empire killed his father. He consistently did more than he needed for a group that didn't trust him and which he had no real ties to, probably even more so than Jyn. Also, their plan probably would have gone a lot smoother if the Rebels hadn't shown up at the end.
Blowing up the tower at the end was kind of dumb too. Apparently this is the only place that the plans for the Death Star are stored, although they still manage to build another one. I don't remember the original trilogy too well, so maybe they got the plans back from the rebels. More importantly, that was apparently the place where ALL the architectural plans for the Empire were stored, for possibly every secret project they had. I guess they don't need those if they have a Death Star. I think it was used to store backups for most things(except the Death Star), so the original plans are probably still available, but they still just wiped out all of their backups.