C'thun and Yogg-Saron as Heroes?, Oh my gosh no, they should be world wide aura, spellcasting buildings. About the factions I would suggest a big 3 vs 3 for the main fight. 2 Demon Factions, A strong hero faction and a main force one, and the corrupted Highborne, would turn into Satyr eventually, for the evil team 1, 2 Kaldorei resistance Faction, Main force with the priesthood of Elune and the Ancients, Treants and Druids (yay treant race), and the Dragonflight for the hero faction counterpart in good team 2. For the remaining 6. 2 vs 2 vs 2 with the participants being: Aqir and Faceless vs Troll Twin Empires vs Earthen and Tauren. The stages: For the 3 vs 3 main fight, the center of the map, and some random spots of the world; For Aqir vs Trolls vs Tauren, Southern Part of the World; For Faceless vs Trolls vs Earthen, Northern Part of the World.