Started a fresh game (instead of an old save file) and Ion Cannons seem to work fine now, so that might have been the issue. However no bombing is doing shit. There is an 2 mio points armada bombing a planet for literally decades, and the Burlust's ground forces are decreasing EXTREMLY slow. Not sure what is going on with this.
I was pretty hyped for the game, and it is ok to have some bugs on release...but the game is out for a week now, get you simulation right. This is really silly. Everygame in Observermode produces a strange result. And I'm trying it almost everyday with every patch.