AAR: The Curse of the Delay

[Imp]

I propose to reduce the turns given in an Advance/Delay generated game by about 20%. This would put a little more pressure on the attacker and give the defender the chance to play a trade-space-for-time game.

As mentioned timed objectives is one way to cause a hurry up or you could just reduce the number of turns yourself to something more to your liking, I usually do or set timed objectives high.
There are so many variables deciding what the number of turns should be is not easy even when you know the force, visibility & are looking at the map.
Increasing AI% to 150 or reducing the size of the map would have made it harder giving you less avenues of approach & making the AI less dispersed.
Look at mainly the height of the map versus number of defenders, they are forced to be spread thinly so allowing yourself the time to advance as a group across the whole map. You said it yourself engaging lone units with 1 & a half platoons being the stiff resistance.