As a frame builder I would not use a braze-on eyelet on a dropout to support a rear rack. What has unfortunately happened in the past was that when the loaded rear rack fell over and the panniers (or tent or whatever) hit something on the way down, the braze-on was not strong enough to stay on the dropout. The force broke off the eyelet. This was an eyelet properly brazed with brass (actually bronze but American builders say brass) and in addition a little miter was filed into the dropout to give additional support and contact area. Even if the rear rack is not usually loaded down so the strength would be more than enough, the possibility exists that someone might make a grocery run and - especially if it is only loaded on one side - the bike may tip over and the force of the fall with the extra weight will break off the eyelet.

What I do if the dropout already has one eyelet is put the rack on that one and the fender on the braze-on eyelet. If the dropout has no eyelets I put a water bottle boss as close as possible to the dropout to hold the rack strut and braze-on on eyelet on the dropout for fenders.