I think you'd really need to post the recipe to get an informed answer. If the three ounces are of hops with low alpha acids, and are added across the boil, then the beer could be fine. Alternatively, if the three ounces are super-high alpha acid hops all boiled for 90 minutes, then it could be fiercely bitter. I don't think 3 oz is a silly amount of hops for a 5 gallon batch - though I'm a bit surprised to see only 6 pounds of grain.