Slayer of the Summoner

Interesting approach. Are you talking about leveling up 7 heroes and sending them out one by one to clear out neutral creatures, defend mines, and rush the enemy? Or is it about passing the army in a chain to 2-3 main heroes?
It's an interesting idea, tell me more.

And regarding hiring heroes...choosing heroes with specializations like Mysticism...Eagle Eye...or something else equally useless...it's almost offensive and I don't even want to...or am I wrong?

In the first week, there are 3 heroes with troops. These troops are needed.
There are several typical strategies for the first week:
1. The army plays, not the heroes. This means the following: a hero fights, passes the army to another, that one to a third - and that one also fights. This greatly increases both the speed of developing your own territory and the ability to push into neighboring territories.
2. Battles should not only be fought by the main hero. Often, certain areas are better cleared not by the main hero, but by another. This other hero can be: a tactician; a mage. For example, Ciel can be incredibly useful in the first week.
Second week.
There are two heroes with an army. The army is needed.
What is the army needed for?
1. Cannon fodder for clearing out difficult areas.
2. Cannon fodder for capturing difficult structures.
3. Cannon fodder for weak mages.

Remember the typical strategy: capture a Castle, build a tavern, buy a hero there, and send them to explore the territory.
Chains are essential in the second week. You need to supply troops/magic from the main base/outposts/other locations. Send weak units into newly opened passages first, then follow with the main force if there's a reason to.

In the third week, the role of chains becomes even more important, and again, 2 heroes with an army are needed. In the third week, you will capture both Strongholds and Hives (if not captured earlier). Without troops, you can suffer unnecessary losses in Hives. In addition, a hero purchased in your home Castle with an army can, on the way, clear out what was difficult in the first week (Medusa lair, Naga bank).

What will be the result?
Due to active gameplay, you will have many resources and a decent number of Castles (of course, it depends on the map). Many Castles mean a lot of gold and markets (potential gold). If the situation is such that building a Guild is really necessary, you can realistically build it in the third week. Or, instead, you can try to win the map.