In many years working in search, there is only few constant things that I observe when we talk about quality. One of them is that: "Data is the king, not algorithms".
If you wan to improve the search quality, quite often you need more data to analyze and you do not necessarly need a better algorithm. The best situation is when you are able to "contaminate" or to "enrich" you data with other information coming from different domains.
So you are working on Web search quality, maybe you can get a huge help from other domains such as News, blogs, Dns, Images, videos, etc. You can use these additional data sources to extract signals used to improve the Web search itself.
In many situation, a more sophisticate algorithm will not provide the same impact of some additional data source.