Walkthroughs for custom maps.

What you wrote is utter nonsense, and as a mapmaker, I would never include something like that in my maps.

I can only partially agree, because:
1) Map authors don't often force us to engage in such battles. Perhaps at the beginning of the map, but that's normal, and there's nothing particularly crazy about it.
However, the examples I gave usually require this to maintain the pace. That is, no one forces you to move your units across the map at a walking pace, let alone a gallop. I completed Wayfarer in 6, 9, and 12 months, even though it seemed like the same map. Therefore, it's easier to defeat the enemy with a larger army. And with a smaller army, you sometimes have to struggle. So, you can simply accumulate strength and crush the computer without needing to get the perfect RNG.

2) There's also a theory of "pseudo-randomness" being discussed in this thread, which essentially states that if you repeat ALL actions on the battlefield with complete accuracy (who, where, to which cell, etc.) and at the same timing, then ALL other actions will be repeated 100%. As far as I remember, the HD+ mod (or its absence) has a slight influence on this. Therefore, if you catch a pattern in the first 2-3 turns, you need an algorithm, i.e., by understanding what will happen on the 4th turn, you can repeat it, albeit with some effort. This is easily verified; for example, if you place Wizards in the 1st stack with the 1st speed, they will cast the same spell. But if they have the 2nd speed in your army, then, depending on how quickly (this is the main thing), and where you place the stack with the 1st speed, the Wizards may already cast different spells. So, with pseudo-randomness, you can catch the desired "randomness," at least in the first 1-5 unit movements. After that, it becomes much more difficult.

P.S. Difficult battles with RNG influence can probably be considered those where it should manifest itself some time after the start of the battle. In the first few rounds (10-30 seconds), this is not very important – you can simply restart the battle. But if you spend a couple of minutes in battle, and then the computer, instead of resurrecting its Phoenixes, casts speed+prayer, and the battle doesn't progress due to speed, or if the computer resists a debuff, then you can, of course, get frustrated. That is, even 5-7 attempts of 2.5-3.5 minutes each is already 15-20 minutes, which is a long time. I can recall a couple of such battles. For example, in Xy'ed, I chose a VERY good terrain for the battle, where you can hide part of your army (this is not the well-known "safe cell"), but you had to play for 20-30 rounds, and only then could the computer either spend mana on buffs for itself (which is what we need) or heal/remove spells from its blinded units (which would kill our archers). Such battles are, of course, mentally exhausting, including because of the time wasted.