At Ball Horticulture, there was a display of Burpee products including something I had never seen before: grafted heirloom tomatoes! Personally, I've never had an disease issues with my heirloom tomatoes, but it's an intriguing idea. I suppose the rootstock may also improve drought stress and pump up production?
From what I heard, these grafted plants were so popular during their test-release last year that they sold out of them online in minutes! For me, grafting an heirloom kind of defeats the purpose of growing an heirloom. At least you can still save the seeds and grow them next year. However, they won't carry any of the benefits of the rootstock in subsequent years.