Funny, everything the OP said I feel about Glen Davis and not Rasheed Wallace. Although Davis does seem like he tries harder though.
How was Rasheed doing poorly last night, outside of a rotation or two? He came in and lit up the Cavs in the post. Is it his fault that they call an iso-post play for Davis, who proceeds to badly miss and fall to the ground, thus leading to a fast break? Is it Sheed's fault that they throw him the ball at the 3point line with 4 seconds left on the shot clock? He had 9 very efficient points at the half, and could have played better in the second half, but so could have everyone else on the Celtics.
While I agree that Rasheed doesn't play 100% every play, and it can be frustrating to watch at times, but he does provide a lot more than a bunch of other players off the bench.