The 8th stage of the annual John Van Caneghem Tournament (2007).

But in reality, this option is quite time-consuming. You need to scout the heroes and check who will be receptive to diplomacy.

Well, this had to be done in all scenarios. Much depends on luck. I happened to find Malcolm early on, so I only had to check the rest on their first two promotions, and after Haart, even just on one. And the hero-finding tool with 15 heroes in the list works almost instantly.

and long battles against slow units (thankfully, the ballista killer works well),

It definitely works well, but it strains your mouse. nwcAres is still better.

and chains for transferring troops.

No one can do without them. What was annoying was the lack of a Ranger among most of the heroes.