Yes. Depending on what you are searching you can end up seeing lots of results from one big site (e-commerce or FB).
Also stackoverflow has a problem and the results are repeated for a lot of queries I do. One URL is for the question and the others I think are for the answers.
Also the more popular answers are coming up over the more relevant results.
Seems like changes that would be valuable for most instances of casual searching, but when it's an off-the-wall blog you've never heard of that has the answer you seek, it's a problem.
Yes, I find Google a bit unreliable for documentation and I feel it's personalized search lets me down. I find DuckDuckgo to be much better for finding documentation and if I want to use google I can always use DDG bang operator !g