As Simon points out, he's among the league leaders in solo tackles by defensive linemen. Clearly he's doing a good job against the run. We certainly do need to find a pass rush, but to say it can't get any worse is completely off base. It can get much worse. Schobel is a good all-around player, and while the aspect of his game thats missing right now is an important one, he still does other things well. We don't know what we would get from a 3rd round rookie, and the possibility exists that he'd be a liability if left to man the position on his own.
I agree that we need to get a look at Ellis. If Schobel, Kelsay and Denney are completely unable to generate pressure, then its time to explore all possibilities, and that means dressing Ellis and giving him some snaps. Bobby April will have to live with one less special teamer on gameday...sorry, Copeland. Ellis should play, but it should be on a rotational/situational basis at this point.