Being human and visiting the world of Dragons would be memorizing and you'd be met with possible trusting issues, visiting the Dwarves, and they would look at you with modest resentment..speaking from past lore here of most phantasy-type games/lore.
Being elven and visiting dragons, you'd be met with possible likeness and maybe a treaty signed for support of both races. Meeting the dwarves, you'd be met with distrust and watched by ones every move in their kingdom..All games are different I guess, but thats how I've come to see it.
And of course, visiting as orcs to both dragons and dwarves..you'd probably be killed on site, as Dragons would think that your there to feed on them, And Dwarves and Orcs have a common hatred of eachother which almost always ends in complete and total war.
Making Dwarves playable would make probably alot of people, (most importantly me) extremely happy, and I understand that this isn't the place for said comment about adding them, I just wanted to point out those little tidbits of info xP I love the way this game looks though.