It's all about the victory conditions, as it stands it's easier usually easier to take every unit on the board except the capital than to take the capital. That's what leads to the game being dragged out way past its natural conclusion. You don't need to stop the runaway leader problem if the game ends when a victor has been decided. Setting good victory conditions that are both satisfying and well timed is always tricky though and I can't think there of any good ones that could be introduced without new mechanics.
A series of losses for one side can tip the balance - especially if one such loss was a lot of your forces. I recently lost a custom campaign because of such a series of losses killing too many of my units. It's hard to say how badly one has to be down before victory is impossible.
Unfortunately there's no way to disentangle the difficulty settings at the moment. If I set Hard difficulty then I pretty much have to forfeit the ability to play the RTS aspect of the game, as the Imperial Army drastically outclasses me.
Yeah, the Hard AI is really smart, but if you're already having problems managing your forces on normal, the enhanced difficulty wouldn't help. Do you think that would change if there were say, only half as many units on the field - both for you and your enemy?
Zolee - According to Swen's blog, they did want to include ground combat, but decided against it almost immediately because they were worried about the AI being too hard, and it wasn't until later that they re-thought it.
It takes a bit of practice to manage skills, but it can be learned. Not every single skill is active, nor are all of them always potentially useful in every battle. You could practice by lowering the difficulty and using groups of Shamans and Warlocks, and practice using their skills.
You can fly up pretty high with the Dragon, much higher than the normal air units can go. It's actually handy occasionally to use with F4 to move selected groups.