Tactics for the Stronghold.

The calculations were based on FizMiG_v.1.14. In total, I played Crag Hack against heroes with a defense skill three times. I lost twice and won once. The strangest thing is that the attack and defense values were always similar, i.e., the difference was +/- 2 points. The armies were also similar. However, subjectively, it seems that sometimes the expert skill of Crag Hack simply doesn't work. I inflict a ridiculously small amount of damage on the enemy. For example, 30 behemoths inflict damage that only kills 3 bulls from a swamp castle. On the other hand, one time when I won, the attack seemed to work, because it got to the point where 60 Rukh hit 60-80 wyverns and killed them in one hit! And the same with most of the other units - one hit and only 20% of the stack remains.... I still can't understand the reason. I always have a couple of levels more than the opponent. Does it matter who attacks first, or is it not important?