In terms of gameplay diversity, I'd also like to mention the Demons. They have many unique perks, and overall, their skill tree is rich... But this applies to the hero's development. However, the starting phase for Demons is completely uninteresting, tedious, boring, and difficult; you just have to catch Ballistas, run around with Cerberuses to avoid slowdowns, and so on. :)
But Orcs cannot offer such a variety of perks and gameplay tactics... largely due to the lack of magic, as such.
Bow down and hear our cry,
Our earthly rulers falter,
Our people drift and die,
The walls of gold entomb us,
The swords of scorn divide,
Take not thy thunder from us,
Take away our pride.
G.K. Chesterton: English Hymnal