When quotes are first posted on the site, they don't have stats. They get solved for a few months to collect averages for time and how often they are solved. You're right; the success rates are usually less than 50%. All the Guests on the site - and the members who don't care about their competitive stats - tend to bring down the averages.
You can't use hints when you're logged in. I wouldn't call it a failure. If you can't solve a quote with all the hints... that's a failure. :P Admin had to stop allowing Guests to set speed records because they were getting very low times on really hard quotes.
Hope that answers your questions.
Slotted spoons don't hold much soup. - Stephen Sondheim