Gameplay tactics on the large map.

Yeah, in this case, the AI calculates everything very accurately and doesn't let you just run away; it positions itself so that it can always reach you.
It's really difficult to break through with 60 Warriors on the third day; the hero isn't leveled up yet, and he can only take down two of them at a time, and he only has enough mana for two spells. So, for the Tribes of the East, this is definitely a bottleneck.