Eichhorn, and others like him, are not good for OLs, in my opinion.
The problem is exactly what you describe, and gets to what I believe is a flaw in the in-game fatigue model. Certain relievers, Eichhorn, Radatz, late-70s Gossage, routinely pitched 2+ innings, and often more than that (check out the IP for Sparky Lyle 1977 at retrosheet.org sometime).
With in-game fatigue predicated upon a pitcher's average IP/G, that same reliever will fatigue rapidly if used more than 2 innings. Result: he'll get shelled. Implication: you can't use him that way, so you'll never get all the IP you paid for at the quality level you paid for.
The same thing is true of pitchers who both started and relieved. A pitcher who started 10-15 games and relieved in 30+ is going to have an IP/G that makes him all but impossible to use as an SP in WIS. Yes you can use him as a tandem, but the point is that pitcher can never be used the way he was in real life.