I'm not sure there's any good way to avoid tipping points, unless you greatly amp up the enemy's power the weaker they get (which makes no sense). It's just something that you have to accept as part of the mechanics of strategy games.
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.
To you people who think the game is too easy by massing units and sending them in, have you not considered changing the difficulty?
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.
