1) Planetary defenses have too much of an opportunity cost. In Civilization, say, building walls on your city doesn't make your city less effective. You shouldn't need to take up extremely valuable production/research space to defend your planets. Instead, have slots along the bottom of the map specifically for defense structures. The only cost there is when they get built. I would also suggest upping their cost some. This means that people will actually build these structures. Currently, I almost never want to use them and that's a shame.
I also agree that Yor extreme world colonization needs to go. You might as well just grant all of those planets to the Yor at the beginning of the game. And it's clear that the extreme planets tend to be awesome planets as well, which is somewhat strange. Not to mention that the Yor AI loves to just plunk in and grab them and then get them flipped.