Just think of Heroes, Elites, Dragons and mages as being unique. You can only have one of the same name in an army. But as many elites as you like as long as they don't have the same name (As in two of the same). Hope this helps a bit.
This example is correct:
"So Basicly I can have an Army with Dragonslayer+Holy Knight+Green Dragon+Red Dragon+ Wizard of the Calm+ Wizard of the Wave"
If I always appear prepared, it is because before entering on an undertaking, I have meditated for long and foreseen what may occur.
--Napoleon Bonaparte, 1831