Discussion of level 1 monsters.

Real battles never take place in "one-on-one" scenarios; heroes and other stacks are involved. Therefore, the value of such "experiments" is highly questionable.

But if you level up the leaders of the faction (Orcs, Centaurs, Archers) as mages, and give Orcs and Centaurs accuracy, they will still be effective in large numbers and defeat level 4 units.

Added 8 minutes later
I remembered one battle that I would have lost, but the Archers saved the day:
So, the enemy forces: a level 15 general, 2 stacks of 5 Titans each, and 445 Dwarves. My forces: 1 level 20 hero (I don't remember who, but he had magic skills), 1 Angel (eliminated early), 100 Squires (didn't bother with them), 450 Archers.
First turn: the general with a crossbow attacks the Angel - it dies.
Second turn: Archers attack a Titan - the Titan is ready, losses of 45 Archers.
Third turn: Squires. Sent them into the fray.
Fourth turn: my hero attacks the enemy hero, deals half of his health.
5th turn: the Titan attacks the Squires, 9 Squires remain.
6th turn: Dwarves.
7th turn: Archers - another Titan is ready, losses of 45 again.
8th turn: my hero finishes off the enemy hero.
9th turn: a Dwarf kills a Squire.
10th turn: Archers destroy 145 Dwarves.
11th turn: destroy another 90 Dwarves.
12th turn: Dwarves try to reach my hero.
13th turn: victory. Thanks to the Archers!
So: even in skirmishes, it makes sense to include Archers, especially if there are many of them!