If your problems are with nematodes or soil diseases, than a different rootstock might help. I'm not an expert in the humid climates but have heard from others in humid states about problems with a blight disease, etc. that I'm unfamiliar with. There is good information at the forums at
Tomatoville® Gardening Forums with folks all over the world posting there. Good luck!
The Maxifort is the most popular rootstock variety and also the most expensive!!! Seeds cost me something like $.50 each but if I bought something like 200 the price comes down a little.