I find it very hard to believe that a professional baseball franchise was only thinking about the present, and not the future. If what you said is the case, then lots of people need to be fired immediately.
As for Vazquez, while he was good in those months, he did so with a ridiculously low BABIP, and his velocity remained unimproved. After what he did in the first two months of the season and with the weather beginning to cool down, it would have been foolish to expect Vazquez's success to continue.
As for his second half, those things tend to fluctuate. All you need to do is look at his first half of 2010, which goes against his career trends. It's possible that he would have struggled in the second half, but all signs pointed in the opposite direction.
Additionally, you can't say everyone thought one of those pitchers would be a luxury. I was on this board, numerous times, stating that I thought the rotation was in a great deal of trouble moving forward, and that failing to acquire Haren was a mistake. The Yankees definitely agreed with this notion, otherwise they wouldn't have been willing to part with Jesus Montero for 2.5 months of Cliff Lee.
When it comes to this offseason, they still would have had the necessary money to go after Cliff Lee. What has happened this offseason proves that, because after all the money they've spent, they still have approximately 20 million dollars left to spend.