B-Ref's career splits show that only 221 of his career plate appearances have come against pitchers considered "power" pitchers (with a .657 OPS). Against finesse pitchers, he's had an .856 OPS among 334 PAs.
That's roughly one quarter of his career plate appearances against power pitchers. Know what's interesting? The NL total splits this year profiles just shy of one quarter of all plate appearances being against "power" pitchers.
So that means not only is the perception of Heisey's struggles not backed up by stats, but his proportion of who he's been facing is right in line with the rest of the league -- meaning he's not benefiting from being utilized any special way according to his strengths.