The number of individuals posting on the forum that understand why they were banned, but are unable to grasp the philosophical and ethical reasoning behind it seems vast. So it’s time for a history lesson and gameplay design rhetoric.
In single player, the maps don’t reset because it’s a persistent world of 1 player. This is true only until you create a new world, then those maps are also randomized.
Online, not only is it different, but it’s competitive. So the map changes. Why does the map change?
Well the most obvious reason is that the map being randomized levels out the fairness of players receiving better maps vs. worse. This way they can reduce the amount of RNG in a more competitive setting, while also keeping a core aspect of the game.
In the original Diablo, one major cornerstone, besides the live action and randomized loot, was the map always being different on each playthrough.
This was such a huge aspect to replayability alongside loot, that they made it a persistent aspect of the Diablo franchise.
If hacking what loot drops would merit a ban, then breaking the second most important aspect to replayability would too.
What you’ve accomplished with MH is a psuedo-drop rate increase by illegally boosting the rate at which loot drops, this is because you no longer have to explore the map alongside your fellow players.
Loot drops and map randomization are cornerstones to the franchise. MH gives the player a clear advantage by removing arguably the second most important aspect to Diablo’s originality. It was always going to result in a ban.
TLDR: if Diablo had a 10 commandments, using MH would break No. 2.