Well they were in the first one, why not the second?
There is nothing like having them assualt a base. However, I believe they should have a slight nerf. In Men of War, soldiers and vehicles have limited ammo. ODST’s lore wise, have limited ammo when they drop and often have to scavenge for weapons and supplies from friendly forces. This would suit Halo Wars 2 since it would add a new area of strategy to the game