as for using the one braze on for both fender and rack, my experience with my aluminum framed Tricross is that it works fine. This bike has only one braze on and I've had a rack and fenders on for four years without any issues, with up to about 25lbs or so in the rear panniers. I used a longer bolt and all has been well. I havent been doing mtn bike touring on really rough roads for days and days on end, and I havent had more than 30lbs on the rack.
As Tarwheel said, my old touring bike with two sets of eyelets doesnt seem to have a diff between the two.

In my opinion, keeping an eye on bolt tightness is more of an issue, as bolts getting loose will cause so much more "bad" force on an eyelet (and dont forget overtightening, I have made that mistake too) Loctite seems to be a really good preventative measure I wish I had done in the past.