I just had a battle with Principes and another spear unit.
The battle took really long and I think the reason was that they were both stuck in reloading/ firing mode for the pilum, Once the pilums where about 25% finished (20 minutes) into the fight they all went into combat stance except for the AI which stood in throwing mode. Now what I observed from this was that due to the units standing there they weren't killing and did not engage even if the enemy unit was behind them. I think if the bug for units that have pilums were to be fixed them the battles would be much smoother. Also another bug was that the starting turn was on Summer, I switched mine to Winter and it seems the CAI is a lot more interactive or it might've just been the update..idk but let's fix one bug at a time!