I dunno, I think they need a fourth high-leverage reliever more, but I don't know if Walker really is that (or can get out LHBs enough). Ross is actually fine for length (and, in fact, had shown signs of being a good high-leverage guy if shortened last year), and Banks obviously needs to be in a more targeted role.
Walker probably should go more then one if he looks good, but then he'll probably fail in the second inning and we'll complain. Right now it would be nice to get that 5th run.