Apparently there was a scene or two with Gurney and his balliset, but they were left on the cutting room floor.
I think Brolin was an acceptable choice for Gurney, but I think Brolin didn't have enough screen time to really showcase the character. There were likely better choices for the role, I agree there, but I don't think Brolin was miscast so much as the film itself just didn't do full justice to the character, yknow?
And I think the makeup was too light. Gurney is supposed to be damn near nightmarish to look at, with that scar twisting his face up. If they had gone heavier on that it likely would have worked.