So you rank people on their stature, something they can't control? Are you gonna then judge a vocalist cause they are fat, or a gril? So Dio is short but he has one hell of a voice. And all of his songs aren't D&D. Ever listen to Magica? Awsome album even better with the 20min story narritive at the end. Dehumanizer isn't very well known to me but I don't recall too much D&D/rainbow lyrics on that. I think people base that stereotype on Neon Knights (a great song BTW) or Heaven & Hell. Sure he uses the word "rainbow" in a lot of songs. But there is diversity. Personally I love his Elf and pre-Elf recordings. Very different but I still like them. Check 'em out here:

http://www.dimwhit.com/dio/mp3/index.html

I really enjoy the tune "Amber Velvey"

P.S. I envy you that you got to see Sabbath on their Dehumanizer tour :)