With the discard effect and the condition of this card, the effect will be only fullfilled when you have at least 5 goblin cards in your hand. I find this restriction for the gain a bit too high, since throught the newly introduced facility gainers have the same effect bur only for a lower condition (I mean, 2 facilitys for the cost of an uncommon, with this card you would need at least 7 goblins in your hand to do the same within 2 rounds). But throught the high spreading rate of goblins i'm quite unsure how this game will work in the game.
When writing this comment, i face that i can't directly know if this card is imbalanced or not in its current form, since we don't know which goblin cards will be used and have effect in the game, but still i feel that this card will be most time not used and other facility gainer, like gateway, will be used, sibnce you don't need much recources in a zero cost/recruit cost deck (And a Goblin deck would rather be one of these)