In case anyone is still unsure about the Nerubian wording, let me put the problem in another light for you, the common sense approach.
There are three possible understandings from the Nerubian cards.
a) +1/+1 for each card of a certain type in your graveyard
b) +1/+1 if you have 1 or more of a certain card type in your graveyard
c) +1/+1 if you have exactly 1 of a certain card type in your graveyard
Firstly the option of
a, +1/+1 for each card of a certain type in your graveyard, is a dangerously powerful mechanic. By the 9th turn, you will probably have, for simplicities sake, 3 allies, 3 abilities and 3 equipment in your graveyard.
This will enable you to have, using
this card, a 4/4 for 1 cost. If you play an ability heavy deck, you will mostly like have 12 or so abilities in the graveyard by turn 9, making a 13/13 for 1 cost.
This is overpowered in this sense, so we can rule this out.
Another option,
c, is that these cards get their +1/+1 for when there is exactly one of a card type in your graveyard. By looking at
this card, we can see it relies on allies. By turn 4, it's very likely you'll have more than 1 ally in your graveyard...and the game currently lacks very many graveyard controlling cards.
By later turns, you'll probably have a lot of allies in your graveyard, making its effect meaningless in later turns,
We can rule this out as being far too situational to have any use of any kind, it would effectively be a blank card.
Since the two are eliminated, all that is left is
b, that they get +1/+1 if there are 1 or more than one type of card in your graveyard.
TL,DR Version :
a is much too powerful
c is much too situational
Therefore, using common sense, the cards must mean
b.