In my opinion, Civ warfare really moved in the wrong direction in Civ5. Instead of evolving towards more strategic-level warfare, they did the complete opposite in Civ5 and moved completely towards inappropriate tactical warfare which humans will always be better at! The only way that the AI can defeat you if with superior numbers but then what's the difference between this and SoD system in essence???
What they should have done is expand on the air-mission model to all combat and make it more a strategic-level decision. You'd setup "armies" or "fleets" just like you do air fleets, then told it where to go and gave it "missions" and rules on what to do upon contact and all action is resolved simultaneously at the end of all turns. Then warfare becomes a matter of strategic-level decision making. How large are my armies and fleets, what are their compositions, where are they going, and what are they trying to do when they get there?
With a strategic-level combat system like this, the AI can absolutely handle it because it is no longer trying to move individual units and fighting with them which it will NEVER do well compared to the human. Instead, it would make strategic choices based on its situation and these it can do well.
Here it would be more about strategic level combat. You would be making decisions like assembling your fleet for Pearl Harbor attack and go! Or assembling your invasion fleet for D-Day and go! Beyond that you would not be coordinating individual units to fight these battles and instead et them resolve themselves with army-vs-army-vs-fleet combat system! No more micromanaging tons of units either as SoD or carpets of doom!
With the scale of civilization, I have always believed that it should have slowly evolved more towards strategic-level warfare and away from individual unit, tactical warfare. To me the scale didn't quite fit and just as importantly any human would always have the edge because a human can always micromanage individual units much better than any AI that has to employ fixed, rigid algorithms to do so.
Of course, many people will disagree with me and want to maneuver units one-by-one and such. And these people of course are loving 1UPT PG style tactical combat. That is fine, it is a valid opinion. IMHO, I just don't think it belongs in a Civ game. More importantly, the AI will never be good at it except through force of numbers. So why not just make it more of a series of strategic-level decisons using units of "armies" and "fleets" with "missions" so that AI does not need to micromanage and can instead be competently programmed to make good strategic-level decisions.
Here the AI and humans decide on how large are my armies and fleets, what are their compositions, where are they going, and what are they trying to do when they get there? Then let the "great generals" take it from there to execute your chose mission!
Of course such a change will not happen for Civ5 and probably cannot be modded in. But this poll can show whether Civ5 direction is generally favored or if people feel as I do that it moved in the wrong direction towards too much tactical level warfare.