Oh the game is definitely too easy. Go with it. The game is supposed to *look* hard, but play easy. The idea is to get people in to the hobby. If you want it harder, just up everything's vigour by 1.5, so Grots become 3, and Deathrunner becomes 20, hah! Or, you know. Field a 2000 point army of goblins against, say, Bloodbound.
The thing with the Brutes as above - if they actually get to take their turn, they will absolutely kill heroes.