I tried overhead sprinkler watering two years ago and seemed to have really good results w/o much disease. That year I planted all OP varieties with BrandyBoy being the exception. That was the best tomato year I have had.
Last year I miracle-gro'd twice and because we had weekly rainfall I didn't water at all. I had all hybrids last year and had lot's of disease problems...but like I said last year was fairly cold in May/June and regular rainfall afterwards...so I partially blame the weather. My production stunk too.
My father in law puts a soaker hose next to the stem of his tomato rows and has excellent production every year even after planting in the same spot.
I think I am going to try the soaker hose setup this year and see how it goes.