What is your definition of the word "suck?" His 2008 year when he went 18-3 with a 2.90 ERA is defined as "sucking?" He had a whole season where he was a solid starter. I don't think you can define that as a year that he "sucked" and a whole year is more than a "brief moment." Past 2008 he has sucked and has been injury prone, so I think that part of what you are saying is true. He was not that great in 2007, but he did get us two wins in the 2007 postseason and one of those wins came in the World Series.
Dice-K is being mentioned in this thread because he is a depth option as a starter. He has sucked this year in all of his rehab starts, except his last one. He actually had a solid outing giving up no runs in five innings. That is after he came off of the DL for the second time. I am not saying that we can be optimistic about Dice-K, but we can definitely keep an eye on him as he continues his rehab assignment in Pawtucket. If one of our current starters gets hurt or completely starts to suck, then it is always nice to have a depth option like Dice-K, especially if he is pitching solid in the minors. We can be optimistic about having him as a depth option.