I think this is pretty common, if you want a website to rank. Then rank it as best as you can then smash the other websites with shitty, unnatural links. Pretty good idea actually but if it continues then it creates a really bad environment for search engines.
Not just a good idea this is actually done already by the blackhat guys, they also use the same technique to extort you in the classic "nice website rankings you have here, be a shame if anything happened to them" manner.
The disavowal tool really isn't that hard to use. Yes, it is more work than no work, but if you depend on a search engine for traffic, you're going to have to do some work to optimize for it (like, sign up for webmaster tools).
