I know they have over 70 actors now (which is awesome) but I think another way they can make more NPC's/races unique is by not having them repeat the same information.

E.g. in Oblivion one voice actor will say a rumour and then for some reason they made another voice actor say the exact same line, if they had just rewritten the line subtly like instead of every person saying "I saw you're fight against the Gray Prince ... bla bla..." some could say "You destroyed that damn Orc in the arena, what a glorious battle" (obviously a lot better than that but you get the idea). Would it really take that long to rewrite these few repeated lines, I mean I know there were thousands of dialogue lines written, but still the actors could even have ad-libbed a couple.

Still from what we've seen the dialogue seems a lot better already so I'm confident they have improved this area a lot.

Trust me, it had everything to do with their lack of voice actors and the fact that they blew the budget on Patrick Stewart and Sean Bean. If they'd had multiple voice actors per race, or (sorry voice actors, I'm not attacking a clearly-overworked bunch of folks) if they'd hired better voice talent across the board instead of putting all the money into two roles. None of the actors they had voicing the rest of the game were particularly flexible with their voices (or the director didn't get them to change things up for some unknown reason), and the result was a bunch of different characters sounding identical (even if, say, they were supposed to have a thick accent).

The increased cast size and the more balanced budget is definitely going to make all the difference in the world. I promise you that if you hear the same exact words from two different actors, you won't even realize it.