I just submitted a new sitemap, which is pretty much the same as old sitemap, with about 10% more URLs. Then I see my traffic dropped 50%. I am not sure what's happening, all my pages are no follow, and there is no error whatsoever in "Sitemap errors and warnings". The Google webmaster tool is no help, it's showing URLs that no longer exist from months ago, or that I am blocking parts that are not blocked in any way. It's a near worthless tool, it's like driving forward by looking at rear-view window. I can't seem to tell what's going on. Anyone have any idea?
I never heard if sitemap can destroying google pagerank. Maybe there are other websites that rank higher than you in SERP.
For one thing, all of your pages should NOT be nofollow. That is not natural. You said 10% more urls, but what number is 10%? Is that 10% of 1, 10% of 10,000, or 10% of 100,000? Its going to take weeks, maybe months before google really indexes the sitemap and crawls all the pages listed in the sitemap. So if your expecting instant changes, do not count on it. Unless there are errors with the sitemap, leave it alone. Give google the time it needs to do its job - and dont worry about it.