Which Orc hero do you prefer?

Nah, Keegan isn't a great hero. Or rather, he's not the best hero. Goblins don't offer a significant advantage in battle, and even if you have 200-300 more of them by the endgame, it won't make much of a difference. It's better to choose someone else. Although, theoretically, you could try to build up a goblin army, and closer to the endgame, use "Protect Us All" (which gives you goblins equal to twice the number of level 3 orcs). Then their number will be truly huge, the Horde's Fury will deal massive damage, and the chances of spell disruption and trap activation will increase. All that's left is to level it all up, but it's not that difficult. And if you also train heroes to level 6 with a mentor, giving them all the orcish warriors beforehand, you'll have thousands of goblin meat! Of course, this is already pushing the boundaries of fantasy, but still...