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Here's the thing about park factors.  They're sued incorrectly.  By everyone.
When it comes to pitchers...the more batters you keep from putting the ball in play, the less the park matters to you.  DNRA solves this problem by only park-adjusting the HR rate per fly ball in play at each park.  Some of the most extreme shifts from career ERA+ to career DNRA+ come from pitchers who pitched their whole lives (or most of them) in parks that are extreme...the Astrodome, the old Yankee Stadium, Coors Field, etc.
Pitchers Parks cause pitchers to be underrated by ERA+
El Sid pitched for the Mets in one of the longest-running pitcher's parks of his time (Shea).
Those low ERAs were EARNED...his K rate and modest HR/Fly rates ensure it.  His teammates less so.  The same is true of Doc Gooden.
Here's SId Fernandez' DNRA+ line:
Year    Lg      Team    Outs    DNRA+   Marker
1983    NL    LAN    19    51    -0.24
1984    NL    NYN    267    99    1.13
1985    NL    NYN    513    130    7.67
1986    NL    NYN    609    114    5.81
1987    NL    NYN    472    109    3.77
1988    NL    NYN    568    127    7.84
1989    NL    NYN    662    127    9.16
1990    NL    NYN    547    137    9.47
1991    NL    NYN    131    141    2.45
1992    NL    NYN    643    132    9.98
1993    NL    NYN    356    137    6.24
1994    AL    BAL    339    90    0.36
1995    AL    BAL    86    61    -0.83
1995    NL    PHI    194    122    2.41
1996    NL    PHI    192    135    3.29
1997    NL    HOU    15    96    0.05
You can see the persisten bias in favor of El Sid...