I'm not sure DFA'ing Giambi is necessairily a smart move. Even at his declined state he still gets On Base at a decent percentage and hits for Power. He has some value for the team. Moreso then an Morgan Ensberg, for example. I guess perhaps DFA'ing Giambi could be seen as a statement move by the team, but it wouldn't be a case of making a move because he's not one of your Top 25 players because he likely still is.
What should happen though is that they should bring up Gardner and they should give Shelley Duncan more of an increased role on the team. While Duncan's numbers haven't been impressive so far, I think it's because he needs more playing time. I don't see what Gomes offers that Duncan can't, perhaps a little more speed.