One problem is the historical issue.

Armies routed a lot back then, and for dumb reasons.

I just read the book The Last King, and they have non-Roman armies routing because units returned from the front in disorder, and the reserves assumed the battle was lost.

In another battle, Rome vs. Armenia, the undermanned Roman veteran routed and killed about 100,000 Armenians....Lucullus the Roman general claimed only 5 Romans died.

So, I think chain routing is realistic. Most times when I lose a battle it is because one key unit breaks and then I get the chain rout. (Though I don't lose very often.)

The best way to solve this problem for the player:

1. AI should build better units and upgrade more.

2. Killspeed and running is too fast. (Though this might help the AI more than it helps the player.)