Don't rule out insects. Have you ever seen what a tomato hornworm can do to a fruit? Eat half of it and a bunch of the plant as well when you're not looking.
In Howard's Texas Bug Book
he talks about how these worms show up at night under a black light. If you can't convince them to leave with a modest application of BT, you might want to go out at night and see if you can spot them this way. In daylight they assume the exact color of the plant and can be there right in plain sight and as huge as your thumb and you still won't see them. It's like a puzzle, once you train your brain to look for that shape, then you'll start seeing them. I usually find them when they leave those little crystaline looking green black poops on the leaves and ground beneath them. Then you know to check out the plant over that debris.
Good luck. My tomatoes are also going gangbusters this year, but I have to get the water right. I'm getting mites on one plant because I think it stays too wet.