For a while, one of the search engines would index more than 600 pages at a single site. Most importantly, they are not able to index databases that many web sites now use. For example, the United Nations web site has databases of very useful documents that you will never find using search engines. Instead, you will have to go to the UN web site and use its search function, which may be quite different than the ones used by search engines. Your best results may not come from a search engine at all, but from finding one good web site that is useful.
Most web sites have a list of links to other related sites.
So if you find one great site on freedom of expression in Asia, chances are good that it will have a list of links to other good sites on freedom of expression in Asia. Many of the search engines can also be used to search through postings on newsgroups. Dejanews is the king of all newsgroup search engines. It can be quite useful because human rights news and actions are often posted to newsgroups like misc.activism.progressive and the relevant soc.culture groups. The best strategy I have found for using search engines is to use as many words relevant to the search as possible.