Even considering that an enlarger is blowing up a small negative many, many times, wouldn't the same sort of DOF apply? Not a direct correlation of course, but when in doubt stop it down as long as you don't have real long exposures?
Bear in mind that an enlarger is really a macro camera with the negative as the subject and the paper taking the place of the film receiving a larger than life size image.
The most critical relationship is between the lens and the negative.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.