Clash dubplates are traditionally cut at the original studio by the original producer, by request of the sound system. I suppose it depends on your definition of "producer". I'd consider the role of a clash selector as part DJ, part A&R - as much as anything, their skill is for identifying talent and making the connections required to get exclusive dubs cut.
Rodigan is such a dominant figure in the clash scene because of the mutual respect between him and the Jamaican music scene. He can get dubs that no-one else can, because he has served Jamaican music faithfully over many decades. Through thick and thin, he promoted Jamaican music in Britain and internationally.
His career speaks more broadly to the vital role that DJs play in musical culture. DJs are the link between artists and audiences. They curate, they encourage, they introduce. What they do in the booth is the product of their work, not the work itself.
http://www.redbullmusicacademy.com/lectures/david-rodigan-20...
This is why I'm not a fan of protecting your playlists as a performer. I understand when some performers have stems or remixes which aren't available anywhere public, but renaming tracks / hiding playlists / refusing to tell anyone "what song that was" always just comes off as a dick move to me.
I disagree with you on not composing or producing - at least at the highest level of sound clashes. I skipped around a bit in the Red Bull video you linked, and each and every song I encountered was re-recorded (by the original singers) specifically for this event with tweaked lyrics denigrating the challenging sound systems of the day, in line with clash norms.
I agree there is tremendous art, but there is a lot of production around re-recording songs. It's a level above just mixing.
I never expected to discuss Sound System / sound clashes on HN - this is a delightful surprise.