From reading all this it appears to me that the one factor that makes a difference is the terrain. I have posted elsewhere of my desire for a terrain map or preview so you can plan the fight effectively. In an open terrain there is not place to hide and no place to get around when you wish to get there. Thus, in an open terrain the distance is crucial and the faster melee troops close the distance the stronger they strike. Once you start putting obstacles in the way the melee troops are at a disadvantage, obviously, as they are actually farther from their targets and the extra distance will mean they take more damage from ranged troops and mages before the melee can get to them.
Now it's been pointed out that you can set up your troops, go see the terrain, and then cancel. Then set up the troops again according to your battle plan. My problem with that is two things. First, I don't like wasting the time (which is one reason I'm not a great fighter) and second, my memory is pretty good but the exact shape and placement of the obstacles is not always remembered when I return to set up my troops again. A simple map of the terrain on the troop selection screen would solve both problems.
In addition, if you use just one type of troop in a battle the order of things is immaterial. However, placing your troops according to a battle plan would mean you might do a lot better if you used at least two types. I tend to put my ranged and mages in FRONT because I want them to attack first.and am willing they be used to draw out the melee of the other side before I send in my slower moving unites. I think this flies in the face of generally accepted best practices and maybe it's why I'm not a good fighter. I'm still learning.
Finally, it would be nice if the computations were easier. Given all the variances to really do well you either have to do it a lot and develop an intuition about relative troop strengths, terrain, strengths and weaknesses, etc (which is, I believe the way good fighters go), or you have to do a lot of laborious calculations, spend the time entering the details of the enemies and your troops for each encounter into one of the various battle calculators. All of which takes an inordinate amount of time and, in my opinion, isn't much fun.
So my suggestions? 1) Get Inno to put a map on the troop selection screen. 2) Give us a easy way to enter the data of our troops and the enemy troops on that screen to calculate the odds of success for each iteration of our troops. This is something every field officer does in any battle in RL (or should, for heavens sake). 3) Once we scout a province allow us to mouse over it to see the 4 terrains and the troop counts of that province to see if we want to attempt it or not. (After all, doesn't the "scouting" of the province suggest in RL we'd have this information?) Maybe these should have been in the suggestions thread but I'm sure if they should have been somebody will move them and chide me for putting them in the wrong place. LOL!
AJ