So after 1.5 months I finally took the time this weekend to try the campaign after only playing MP before and I don't really understand what people are so upset about, the campaign is really great except 2 major quirks:
1) The AI is constantly circling my around my provinces on their fleets, it is like every faction is swarming around me like an angry swarm of wasps but they do not attack or anything, but it makes me feel paranoid. Or is this actually really brilliant AI programming that aims at keeping you all the time worried so you can't deploy all your stacks overseas? Perhaps the AI is now so smart that it understands human psychology and even engages in psychological warfare?
2) That factions are not destroyed when last settlement falls and that is really annoying when fighting desert factions that can move unhindered everywhere...
3) Why is it that the game in campaign slows down to an unplayable crawl when it rains? In MP it runs fine when raining. Also the constant crashing is sort of annoying, one time I lost 2 hours of progress.
Otherwise the game is really great I suppose.