ooo I don't wanna tempt fate, as I haven't any rust yet! Last year my leeks and garlics were smothered very very early on. This year, even with the dreaded rot, things are marching along and all looks very strong and healthy.
The over all yield didn't seem to be reduced by the rust (the rot does that for me :-\) but I did start pulling the garlics sooner than I would have only because they started to become really poorly and weak, and the rust spores seemed to be dropping all over the ground around the plants and I became concerned that this could over winter in the ground! With my leeks I just removed the first couple of layers, and the inner flesh was fine. ooooooo am I tempting fate now!!!!