To a certain degree, your observation about 'cold call' letters have some validity, but this tends to be most applicable for the top level DI programs (and I mean elite programs). As a means to give substance to an outreach effort, I always recommend that emails include video or links to video. The video will get a look because coaches would rather watch t.v. than read a book.
For the overwhelming majority of collegiate volleyball programs, we can't afford to 'not look' at a recruit who contacts us. The point of the PSA outreach effort is to get onto the 'to see' list of the collegiate programs when they head into the tournament to do evaluations.
Because the recruiting process has become so accelerated for VolleyPSA's, college coaches can't just arrive to club tourneys with a blank sheet of paper. We have to arrive with a list of players to evaluate, who arrived onto our 'to see' list by their own outreach efforts, by a recruiting service, or because we saw them a season earlier at a tournament and need to see how they have progressed.
With the speed and anonymity of the internet, there should be no hesitation for VolleyPSA's to reach out to collegiate programs. The worst thing that will happen is the college coach will just hit the delete button. The best thing that will happen is the coach will want to see the PSA at a tourney. Collegiate coaches are used to getting initial contact emails and we do not view these as desperate, but rather recognize the VolleyFamily is putting in the effort to manage the recruiting game.
I have my suspicions of the PSA questionnaire which is found on the website of collegiate programs. Some schools I have been a coach at, the questionnaires were not very timely in their delivery back to us and I don't think they really capture the technology of today (like video). It is better to contact the coach or assistant coach directly via email and have your resume/video as an attachment; if the programs wants you to fill out a questionnaire for their records, then they will send you the questionnaire or the link to the online version.
In terms of the percentage of scholarships provided to initial outreach athletes, that would be hard to remember. But, I have awarded enough scholarships to such PSA's to know it is worth the time and effort of the families to do this (either themselves or through a recruiting service).
During my NCSA Recruiting Education Talks, I reference two main topics - The significant increase in the number of talented players and the reduction in collegiate volleyball operating budgets have changed the recruiting game these last five years. Families and college coaches can leave no recruiting stone unturned!