Final score have nothing to do with losses during game, and in my opinion it`s to simple. It takes in consideration hero lvl, quests, and days spend playing. There is no pet dragon lvl, or battles fought, or anything related to play style. They should modify final score formula.
And about using weaker unit, there is benefits for them : guardsmen gives +1 moral to archer/swordsmen , royal griffin +1 moral to humans/elves , rune mage +1moral to mage type units , dryad and ents +1 moral . . . So there are bonuses to use certain combo of units, only thing is do you want to, or not.
Also orcs have nice combo : goblin shaman recrute goblin/catapult , ogre recrute orcs , for every blood shaman in you`re army orc chieftain spirit strike gain +1 astral dmg.
I like what dev`s did in Crossworlds for orc race , but making new beneficial relations in WotN would be great : royal snakes give some bonus to other snakes and poison spiders , royal thorns to thorn warrior/hunter , ancient ent to other plants , etc.
There are many things they can change in, but there will always be some ppl that like those ideas, and some at dont like them. And there modding comes in play
Open editor, and with some patience and effort, you can make yourself almost anything in this game. So until WotN, have fun ppl