Here are, IMO, the best three decks you can build, simultaneously:

Orc/Skaven Blitz:

3x Veteran Sellswords

3x Spider Riders

3x Crooked Teef Goblins

2x Lobber Crew

3x Clan Rats

3x Gutter Runners

3x Clan Moulder's Elite

2x Greyseer Thanquol

3x Poison Wind Globadiers

3x Rat Ogres

1x Grimgore Ironhide

3x Warpstone Excavation

3x Contested Village

3x Choppa

3x We'z Bigga!

3x Pillage

3x WAAAGH!

3x Troll Vomit

Dwarves:

3x Errant Wolf

3x Dwarf Miner

3x Dwarf Cannon Crew

3x Zhufbar Engineers

3x Dwarf Ranger

3x Durgnar the Bold

3x Gurni's Elite

3x Troll Slayers

3x Mountain Brigade

3x Contested Village

3x Keystone Forge

2x Master Rune of Dismay

3x Grudge Thrower

3x Innovation

3x Stand Your Ground

3x Burn it Down

3x Demolition!

Empire - "Jumping Jacks"

3x Huntsmen

3x Warrior Priests

3x Pistoliers

3x Nuln Tinkerers

3x Johannes Broheim

3x Contested Village

3x Shrine to Taal

3x City Gates

3x Contested Fortress

2x Abandoned Mine

3x Contested Stronghold

3x Gate of Sigmar

3x Iron Discipline

3x Will of the Electors

3x Twin-tailed Comet

3x Forced March

3x Judgement of Verena

The only card that "overlaps" is Contested Village, but you have 9 of those, so no problem. You could actually run Orcs without the Skaven and build a 4th deck; Chaos/Skaven. But then you'd have to move Contested Villages between decks (because obviously, that one runs a full set too).

Those are all good decks, but I would not call them the best. Not because there are better ones, but because there are lots of decks that can have a fair chance against them.

The weakest of them is the empire one. Sure its got the three judgements and twin tails, but with the shrines and gates and low unit count, its not leaning strong enough one way or another. Its a very good deck, do not get me wrong, but it could be focused more one way or the other.

Where is the snipper deck? A good chaos snipper deck can beat any of those decks, not all the time of coarse, they are all fast enough they can get the jump on the chaos deck, well maybe not the empire deck, then its can always get an early twin-tail, verna opener.

I agree on the contested village, you can;t go wrong with it any deck. With so many things costing 2, getting that extra support down on turn one can be so big. Also you are right about skaven, you can make a faster, deadlier skaven chaos deck, and still have enough cards to keep the orc deck from skipping a beat.

Getting back to what makes a deck "better" You could also go the orc heavy hitter, boosted by damage route, especialy with the new cards and that new orc hero, fit in some orc archers, yes I slowed the deck down a lot, BUT can give it more tactical options, enough to deal with the fast orc deck, and run it down with heavier hitting units. Get a arrow boy in the battlefield turn three or 4, a big'un anywhere else, and you can snip those crooked teeth and siper guys with shoppa right down, force the rush orc to play to quest to get the draw he needs, as now he is running out of cards, and stablize the situation.

Not bad decks, but they could be improved I think.

For the orc deck :

If you go on the skaven-orc route then Where is Bigga is almost useless, at least compared with Chittering Horde.

Lobber Crew should be an auto 3, as he is one of the most dangerous 2 cost creatures. 3 Troll Vomit seems too much for rush.

Agreed. 3 troll vomit is overkill for a rush.

Also yes on wes bigger, it goes in a heavier pure orc deck.

Nice decks; here's what I would change:

Orc:

As has been said, Lobber Crew #3 is good.

We'z Bigga is killing everybody in the deck except the one
Grimgore.

Greyseer is big and he dies easy; I'd run 3. Prolly not going
to hit five icons for Grimgor.

Rock-Lobber is a must with all the guys that can become useless
due to corruption, and the Sellswords. Remember you can do it
once on your turn, then once on their turn. Or more if you have more than one.

Seduced By Darnkess + Mob Up are better than Pillage here.

I wouldn't play any Troll Vomits. It's rarely going to set the board back to neutral because you have virtually no supports. Even with cheap guys, it's tough to rebuild from nothing after spending four to wipe.

Dwarf:

Very similar one of my Dwarf builds, and a good starting place for anybody.

I think the 3 Burn It Down is overkill.

I think you need a few big dudes like the Ironbreakers.

Prolly could do with only one or two Grudge Throwers. I like Armouries for another card that the Cannon Crews can hit.

Empire:

Going heavy support has pros and cons, but I think this is a few too many in any case. I'd sub out the Countested Fortressses for Reiksguard Knights, at least. Playing more units also gives you some hope of winning the game if Verena doesn't go off as early as planned.

I think Innovation is too good to get away from with City Gates. You need a pretty big resource total with deluxe version of the Verena combo (Comets and Marches).