Which study are you referring to there? the EPIC study was published in the European Clinical Journal of Nutrition. I'm not sure why you would find that source questionable. The study found only a very small association between vegetable intake and cancer risk, and that was in the context of an unhealthy diet.
Legumes won't ever be healthy unless there is a huge about face and somebody finds out anti-nutrients, enzyme inhibitors, lectins and phytic acid are good for us. I'm quite confident that won't happen, unfortunately.
I'm unaware of single randomized trial which show the benefits of any of these supposedly fantastic compounds like antioxidants and phytochemicals. I have read plenty of things which suggest the exact opposite is true and they are useless.The fact that people can survive quite well living on nothing but meat and fat is a good indicator of unimportant fruit and vegetables are in nourishing and protecting us.
Any scientific report which suggests using soy and whole grains to improve health as one of your ACJN links does, should be treated with major suspicion. The evidence against those things is well established.
Ornish is considered to be something of a comical figure amongst many serious health bloggers and doctors. The research he uses to 'prove' the value of his formulated diet contains a gazillion other variables which he fails to account for, for example the subjects in his trials also stopped smoking and took up stress relief activities at the same time as embarking upon the diet. His diet was put up against Atkins and the AHA diet a few years back. Atkins came out on top in terms of weight loss and overall health.
http://med.stanford.edu/news_releases/2007/march/diet.html