Here's two things that would give AI a great boost in combat and invasions, two things that since release people have noticed aren't balanced but there's yet no improvement to them:
Remove ships runnnig over embarked units
So many times a superior AI fails it's amphibious invasions as human player simply criss-crosses over it's units and sinks them with a caravel. They should get a combat strenght so naval combats and invasions would become way more exciting and fair to AI.
Remove instant heal
By timing the instant heal promotions, human player has again a big advantage over AI who can't use it as well.
These two things are ones that give the biggest boost to human combat in my opinion, I really really hope that devs consider this, I think they have done great jobs with patching and I sincerely feel removing these would be A LOT easier than just improving AI tactics.
Remove ships runnnig over embarked units
So many times a superior AI fails it's amphibious invasions as human player simply criss-crosses over it's units and sinks them with a caravel. They should get a combat strenght so naval combats and invasions would become way more exciting and fair to AI.
Remove instant heal
By timing the instant heal promotions, human player has again a big advantage over AI who can't use it as well.
These two things are ones that give the biggest boost to human combat in my opinion, I really really hope that devs consider this, I think they have done great jobs with patching and I sincerely feel removing these would be A LOT easier than just improving AI tactics.