I like the whole concept but you have to understand that after a certain points of height the monsters simply can't "target" properly. Now your orc is fixable logically wise all you have to do it bend his back a little bit when he try to his a target but then again you will have to make it so it hits the dwarfs if you want him to look more "realistic" sadly i don't know how to do this but like i said take for example Antharas, Valakas, Baium etc. they are huge and their targeting/attack animations are wacky.