Yeah, I can't think of any statistics that keep track of failure. The only quests I think you can fail are gathering leves, but that's pretty hard to do if your gear is up to date. And even if you do fail, it's definitely not keeping track.

The only place that keeps track of any statistics are third party sites where people upload parses (taken with third party software). But people generally only record endgame content and nobody is gonna hold anything against you in normal content for your parse, and I've never actually run into anyone who looked me up to check my parse in what savage content I have done with pugs.