Pollock (with ball) is a little like Tendulkar in that - in his first 6 years, at least - he was so sensationally consistently superb that it was easy to miss the fact that far more of those performances than not completely changed his team's position. There was no "standout" either (well, there was, but the match ended in an unsatisfactory draw).
Also like Tendulkar, he has the handicap (performance-assessment wise) that he had someone else who could match the superlative nature of his performances. In Donald, in fact, he had someone who could better them; in first Azharuddin, then Dravid, Tendulkar had two people who could merely come somewhere near the same plain.
Players like this - Herbert Sutcliffe is another, and Kenny Barrington, and Everton Weekes - are almost always bound to get less credit than they deserve, at least from those who assess performance by the narrow-minded "matchwinner" criteria. Those who were obvious standouts amongst, if not mediocrity, then merely good - the Lillees, the Laras, the Pietersens for instance - are always going to get this credit for having the chance to, occasionally, completely alter the course of a match almost entirely by themselves. This is a chance denied those mostly surrounded by excellence.
And on the few occasions, between 2001\02 and 2006, when Pollock may have had those chances, he was not the bowler he had been in his heyday.
But rest assured, South Africa would almost certainly have done far, far worse without him in almost every single Test in the first 6 years of Pollock's career than they did with him.