You're meant to play it at M/M, so don't sweat it if you're being battered.

If you're as experienced as you say you are, you should have no trouble though. Just remember, you need to build a military occupation first after taking a city, then the highest government able, or if in the case of a choice between a type 3 or a type 4, pick a type 4 if it's a particularly unruly populace. Government systems were the hardest thing for me to get my head around.