I would say atleast 60 to 70 percent of sites can be taken down with well planned negative link campaign
I would disagree with this. It does not have to be well planned at all. Probably 1 or 2 Fiverr spam link gigs will get most sites with natural backlink profiles moving downwards. Remember, most natural backlink profiles are normally very weak and easily tainted with minimal effort.
The disavow tool has allowed Google to dramatically scale their manual review team at the lowest possible cost. Right or wrong, the disavow data Google receives from ordinary webmasters will be used at one point or another.