I think the point is less about luck than it is about volatility. With few exceptions, the top hitters usually hit as expected and avoid injury as well. With notable exceptions like Abreu and Tex, the best hitters usually don't disappoint (the list is huge for good hitters who have played up to expectations: Pujols, Hafner, Ortiz, Manny, Wright, etc., etc...) The disappointing ones are guys like Delgado and A-Rod and they aren't that bad. Also, Derrek Lee is the only top notch guy (that I can think of) who has had an extended DL stay.
The same can't be said for starting pitchers. For one thing, injuries are much more of a factor for this group (and probably always will be). Top 10 guys like Sheets, Prior, and Harden have missed the majority of the season and others, like Pedro and Oswalt have missed time as well. Other aces going into the season (like Peavy, Felix, Buehrle, and Willis) have fallen far below the high expectations of teh managers who had to draft them in the first few rounds.
As a guy who counted on Sheets and Patterson to be his #1 and #2 pitchers, I know the crapshoot SPs can be. My two best starters have been Lackey and Capuano, who I drafted in the second-last round and scooped off the FA list, respectively.
In the future, I will be drafting batters early and often and leaving the guesswork of SPs till later. It's just common sense I think. In my shallow league, guys like Liriano, Verlander, Bonderman, Jered Weaver, Clemens, Capuano, Arroyo, Rogers, Penny, Ervin Santana, and Bedard have all been added for free off the wire. That's a pretty good rotation if you could scoop up a number of those guys. If anything, having weak pitching coming out of the draft allows you the flexibility to act on breakout arms.
By comparison, rank the best 1B in the game; or the best 2B or OF. I'll bet your current rankings are fairly similar to the ones you compiled at the beginning of the year. The same simply can't be said for starting pitching. In addition, top end bats retain their value for longer than SPs. I think you'd have an easier team getting a good return on Teixeira than you would on Peavy.
I wouldn't even necessarily subscribe to the "get one ace" theory, because at the beginning of the year, Sheets or Peavy could have been that ace. Next year, I won't make the same mistakes again. I won't be rolling the dice on pitchers on draft day.