It's all fine and dandy saying "Don't attack where you can't win." Yes, that's the facepalming obvious conclusion to the current, broken system and the very thing I'm criticizing! My point is only-attacking-when-guaranteed is a luxury you only have because the AI doesn't mobilize its armies properly and station them where needed in due time - if it did, your genius strategy would drop to the floor and could no longer mask how unbalancing the overpowering advantage of the defender is. There is no way you're going to win with six units against 12 unless you are wildly superior technologically or otherwise, and it is unfair to hinge this unbalance on the AI's inability to play the game properly. Thus, we conclude that the game is unbalanced and that there is indeed a real issue for StarDock to resolve here.
Now you're saying I can only take a city if it's not well defended? Wrong. All I need is better troops or a kick-a** mage. However, I really would like to hear your "solution." All I've heard so far is make the militia stronger (hello? are you listening to yourself?) and let me retreat (which you can already do if you choose that option).
If you don't have either superior numbers or superior tech or overwhelming magic, you shouldn't be able to capture a heavily fortified enemy city. There are many times when I delay my offensive until I get that key tech advance that will give me the edge I need.
One thing we can probably agree on is how militia are handled. For example, for the player, they only get their militia in the first battle even if they are unharmed. Are you saying the computer gets their militia back even if they are killed that turn? (I wouldn't know; I've never attacked a city more than once in a turn.) If so, that's wrong. Militia shouldn't disappear unless killed, and they should come back at some point but certainly not the turn they are killed.
However, I maintain cities aren't too tough to capture. Also, they should be hard to take in any game. In fact, I will suggest not only is the system not "broken," it's actually brilliant. It is harder to capture cities early in the game compared to later; this is a good thing! It makes difficult the early rush strategy that has plagued many 4X games since they were invented. Remember having defensible cities works to your advantage, too. It gives you a chance to eXpand and not be eXterminated before the game really gets started.
Yes - the game is much too black & white in siege combat as is where you have to be able to guarantee a victory before you attack. The system I'm outlining where it isn't so all-or-nothing would make the game much more interesting in this regard. It should indeed precisely be possible to take "risks" or, if you will, make partial attacks on cities. The very fact that the city militia instantly respawn at full strength on the very next turn after an unsuccessful siege no matter how many of them were killed should be enough to make anyone see that something is awry with the current system, but I digress.
The game is NOT black and white. You are welcome to take risks and fight close battles. The game let's you do this. I am merely suggesting it isn't sound military tactics to do so. In fact, the game actually does let you take risks much better than many other games. If I attack and lose, I don't lose any heroes or sovereign permanently. And while it hurts to lose experienced troops, you can certainly recover. In contrast, I remember an otherwise fun old game called Panzer General where if you lost a couple of your 5-star troops, the game was essentially over.