If you think repeating that bit of your post answers my point, we're talking past each other, so let me try again
The question is not "you can still tell individual units where to go." It's that if there are going to be, as IME there often are, numerous occasions when I do need to tell individual units what to do, what is the point in me putting them in an army in the first place when I am only going to be giving them indvidual orders agin and again and again down the line ?
In order to answer that question I would need more specifics on how exactly the battle system in Civ 5 would look with armies.
For example, in many games with armies attacking an army of 10 units with 1 unit is a suicide run that gains you nothing. In situations like this maintaining individual units throughout your empire is a waste of resources, and you are better off concentrating your forces in a few large armies. In this situation moving individual units around would mostly be done when you produce a new unit and wish to move it to an army, or if you need to shift strength between armies. For example, if one army is 10 units and the other is 8, and you would prefer two 9's you could send one from the 10 to the 8.
Another way of looking at it is to consider group movement in Civ 4. You take units in and out of groups right? Well imagine now that groups are clearly listed and organized, and that you can easily shift units from one group to another. That's a basic army system right there.
I'm willing to be persuaded here; have you any specific examples in mind ?
The most relevant one I have experience with is probably CtP, Civ's bastard cousin. In that game you could group units into armies as large as 12 (I think, memory's a bit fuzzy.) When two armies fought infantry units would line up across from each other, with cavalry on the wings and artillery in the back. Units could only attack units directly in front of them. If one army was larger than the other army the cavalry could "flank" which basically meant you got an extra 2 units to attack with. All this was done automatically by the computer.
Attacking a single unit with an army of 1 infantry, 2 cav and 1 artillery then meant that you would have all 4 units attacking that 1 unit at the same time, which in turn meant that you would win with no losses usually. What this meant was that the current Civ strategy of leaving one or two defensive units in each city was kind of a waste. Those units were just going to die if attacked by a real army. In comparison in Civ they would probably kill a couple attackers before they were worn down.
So questions you can ask yourself are how much artillery should I use? How much cavalry? How much infantry? Do I want all cavalry armies, to take advantage of movement bonuses?
That game also featured artillery bombardment, a bit like Civ III with the collateral damage of Civ IV. So you could sit outside a city, bombard a couple turns, then attack.
The Paradox games (like Europa Universalis) work basically the same way, except that you can put as many units in an army as you want. If you have 100 regiments you can stick them all in the same province if that's what you want. The downside is the attrition system in that game, which penalizes large armies by killing portions of them via disease/starvation. Coupled with a war exhaustion system that led to major revolts if too many troops died during a war this was pretty nasty. Thus you have other interesting questions in addition to those present in CtP. Do I want to combine my forces into one large stack for battle? Or should I split my forces to minimize attrition losses? Should I confront my enemy, or avoid him and hope attrition weakens him?
Then there's the Gal Civ model. In that game fleet size was limited by your logistics technology level. In that game you had to ask yourself the question, "do I want to research another level in weapons tech to get better ships, or another level in logistics to get larger fleets?" You could also ask "do I want a large fleet of small ships, or a small fleet of big ships?"
Then of course in all these games there's the usual strategic concerns, do I concentrate on this front or on that front? Do I concentrate my forces or spread them out?
