Nofollow links have ABSOLUTELY NO EFFECT for rankings.
Nofollow links are just for traffic, don't affect rankings in any way. Nofollow links were invented to stop the SPAM in Wikipedia, that's why all wikipedia links are nofollow.
Nofollow is not for diversification, diversification is different anchor text, like "your anchor". "anchor your", "http :// youwebsite. com" and different links format like from text, image, frame, redirects... different font types, bold, lists... different domains, hosts, IPs, locations...