I agree here.
Mesoraco has a BABIP of .228 this season and .217 for his career, despite line drive percentages of 16.5% and 16.2%, respectively. I think the quick and dirty math for xBABIP is LD%+100, so his xBABIP would be around .265 and .262, which would add quite a bit to his current slash line of .209/.288/.348, taking it up to maybe .250/.325/.400 (if almost all of the new hits were singles, which I would doubt given Mesoraco's pedigree).
This, plus the fact that this season Mesoraco has improved his plate discipline from last season and is now almost in line with his 2011 minor league year- BB% of 9.6, K% of 17.5 against his 2011 minors totals of 10.4% and 16.6% respectively, I think that the "bad luck" argument is a very valid one here.
Bad luck, when coupled with a rationalization for not playing more (he catches "his guys," catchers don't pinch hit, etc), is not a recipe for getting a chance to prove that bad luck is a reason for lackluster numbers at the plate.