I'd like to know your location, Anonymous. Here in NE Ohio, we've also had an abnormal lack of sunshine, our August has been in the 70s and all days have been cloudy so far. (It's August 6). July hasn't been much different, short one week.
In terms of seed, it was purchased from Baker Creek Heirloom Seeds, a solid company. In terms of staking, all of my plants were pruned of suckers and are about six feet tall. The plants are beautiful and the tomatoes are beautiful. The beds are also covered in weed block, and some with black plastic, so warm soil and germination are not factors. Remember that when plastic gets drenched, water goes through it, too. Next year, I may try the red plastic for better sun reflection, should we get any sun out here!
I use black plastic mulch in the melon beds too, but the continued dampness, coolness, and lack of sun seems to have triggered wilt. Friends and neighbors are losing their vine crops to wilt, too.
I still think that the folks at Cornell are spot-on in this case of weather and its importance to tomato taste.
Neighbors are getting no tomatoes at all - they're ripening at an extraordinarily small size, bitter, and with a tough skin. Perhaps, I should be thankful - my tomatoes taste great when I put them in the dehydrator!