I have been a technical writer for quite some time. Most of the times I found that the quality of end product was not good because we did not follow the standard document development life cycle. I do not think that we need star writers to produce quality artifacts. What we need more is adherence to processes.
After the requirements and information gathering, define the outline for your document which is the table of contents or the TOC. Did we get that TOC reviewed by the technical team to see that it covered everything? More often than not, I have not seen that happening. We just create the TOC and start plugging in content, to be caught very late in the cycle that something was amiss.
Did we do two rounds of technical review, or at least one extended round of technical review to catch the technical errors? Did we give proper guidelines to the technical reviewers as to what to look for? Did we tell them not to comment on grammar and style but just to limit themselves to looking at wrong and missing technical information? In one of the biggest MNCs that I worked for I saw this happening.
Did we do an editorial of the final document after incorporating all the review comments? This will take care of all the writing errors that may have crept into the document, just because either the writer was not a star writer, or by plain inadvertent error.
Finally, if required, did we do a legal review, if the document has legal implications?
Just as a software may have a hundred bugs despite good programmers, a technical document may have errors despite good writers. So all the reviews and fixes are just like testing and fixing the document, if we draw an analogy to software development.
I strongly believe that it is processes, and not writers that matter so far as the quality of the artifact is concerned.
My 2 cents.