"In Honor of Our Fathers"; - "Wisdom of the Earth" [Campaign 3, Mission 4]

I used auto-battle; the losses were 1 goblin, while the enemy lost 3 titans, 6 colossi, and 200 water elementals.

So, I completed this mission, spent some time tweaking the mentor's skills, and spent about 30 minutes reallocating skills to achieve the desired balance. In the end, my Kujin now looks like this:
Expert in Wrath of Blood + Strength against Magic + Memory of Our Blood
Expert in Attack + Battle Frenzy + Retribution
Expert in Leadership + Recruitment Bonus + Battle Craze
Expert in Luck + Magic Resistance + Barbarian Luck + Soldier's Luck
Expert in Diminishing Darkness + Weakness
Basic Defense

There's a bug with Barbarian Luck; it always reduces stats by 5%, making it a useless skill. Soldier's Luck doesn't provide much benefit to an Orc. I didn't take Luck and instead focused on developing Fire Fury. Orcs have a bug where skill resets leave them with bonus stats, so I didn't want to exploit that bug, and I also enjoyed developing Blood to level 3. The Attack skill provides a small bonus, so it can be left as is and developed. It's useful to max out Defense and take Endurance. Instead of Weakness, take Hold. Strength against Magic isn't a very strong ability, so it can be skipped. That's the ideal setup. In general, Kujin easily wins the final battle; I really don't understand why so many people have problems with it.