Recruiters are recruiters - if I was trying to hire for a position in a discipline I knew nothing about I would probably default to qualifications as well.

Get someone with deep skills and has been round the block a few times into the interview who has both formal and good experience (if possible) and really have a general conversation on databases for an hour or two. Go light go heavy encourage discussion  bring the conversation on and off topic see how the applicant responds see their flexibility see if they can react to what you are saying see if you can react to what they are saying.! I can see why you have these set questions as a starting point.

Its a relevant topic so a reasonable starting point and way better than "give an example of conflict in the workplace and how you dealt with it"

PS you are talking to someone who is after the fact trying to get some formal qualifications - I am enjoying the study and it is definitely more enjoyable to study something you have good experience in I am certain it is significantly improving my skill levels. If someone can learn everything without this great but for me I feel it is vastly increasing the speed of my learning in fact I don't think I would have ever learnt some of this stuff without formal study.