The trouble is without the right amount of low cost cards the big dogs will never see play.
You need a reasonable amount of cards that cost 3 or less resources with only one loyalty symbol on the board.
Our play group has dubbed these First Turn Cards(FTCs)*.
In order to create a balanced deck you need to have a large foundation of low cost cards to allow you to start gaining cards and resources early.
This is why cards like Warpstone Excavation(a zero cost neutral support card that provides 1 hammer) are on the restricted list.
Warpstone Excavation is a free hammer that when played early can net you 5 - 7 resources or cards within the scope of a game.
Low cost cards are huge in helping you develop a board presence before your opponent.
Below is my Dark Elf / Undead Deck I plan on taking to Gen Con for the tournament.
This deck works off sacrificing its own units for effects so it has a bit more low cost than most, but it still serves as a good example.
Units(number x cost + loyalty, bold denotes FTCs) 3 x 0____ Veteran Sellswords 3 x 0 + 1LWalking Sacrifice 3 x 1 + 1LDark Initiate 3 x 2____ Crypt Ghouls 3 x 2 + 1LDwarf Slaves 3 x 2 + 2LThief of Essence 3 x 2 + 2LVile Sorceress 3 x 5____ Wight Lord 3 x 6 + 3L Monster of the Deep 21 FTC Units Support 3 x 0____ Warpstone Excavation 3 x 1____ Contested Village 3 x 2 + 2LSlave Pen 12 FTC Support Tactics 3 x 0 + 3L Lash the Prisoner! 3 x 1 + 2L Dark Visions 3 x 1____ Warpstone Experiments 2 x 2____ Burn it Down 3 x 2 + 2L Sacrifice to Khaine As you can see, out of a 50 card deck 33 of the cards can be played on turn 1 to gain me resources and cards for future rounds.
That is 66% meaning 4 - 5 cards out of my opening hand are likely to be playable not counting the mulligan.
Dark Elves are an extreme example as I stated before since many of these units are sacrifice fodder.
As a generic standby rule I would use the following numbers as a starting point: 26 units - 13 FTCs 12 Support - 9 FTCs This gives you 22 FTCs comprising 44% of your deck.
On your first draw, 3 of your 7 cards should be playable not counting your mulligan.
When you start thinking about the odds of drawing the cards you need the importance of a 50 card deck becomes even more important.
Always keep this in mind when building your decks and be selective when choosing your cards.
You can always take it out and try something else, but throwing a bunch of cards together isn't really giving any of them a chance.