Our landing page is actually converting pretty well, at >5% conversion rate (visit-to-trial signup). The problem is that I'm not sure if the right people are converting. We have no indication on the quality of those signups.

If you are willing to help me out, I'll send you an email with my website, so that you can give quick thoughts. I would say the things you pointed out are generally fulfilled, but I may be wrong and biased too.