Marte's career ERA is 3.47. That is more relevant than his ERA in a small sample size with the Yankees.
As for Logan, almost all of his success has come in low leverage situations, and the few times he has entered in big spots, he has either given up runs, or had to be bailed out by other members of the bullpen after putting runners on base.
With Joba, you already admitted that he probably maintains his current level of performance, and what he did during 2008 and 2009 is irrelevant because he was a starter for the majority of those two seasons.
These are not reasons why the Yankees have been able to overcome injuries and slow starts.