As a minnow I never took the time to really review and try to vote for witnesses, but yeah hearing they reject their responsibility is frightening.

I guess checking who is really contributing to the code or at least helping to solve issues on GitHub could be a good start, because you can't possibly audit a blockchain code if you never looked at it even a little.

And there is only 56 contributors to the Steem core repository, that's not a lot. Here are some stats about who contributes the most on the repo, maybe this could help :
https://github.com/steemit/steem/graphs/contributors