I agree, MK on release was too strong. Working out if he was strong because of his kit, his numbers or quite simply people not knowing how to play against him is the hard part. It's not like when Bristleback or Techies were new, plenty of people who'd played Dota 1 knew how what they did and how to deal with them and the knowledge spread to players who didn't know very quickly.
A completely new hero adds an extra set of variables that are harder to assess than just raw power. I disagree that it was MK's raw power alone that was giving him huge laning advantages. Thats not to say it didn't play a part, but it's not the whole story. I don't think we'll really know how much was MK's power and how much was his opponents inexperience until he's added to Captains mode and gets into pro play, it's about as close to scientific conditions as you can get.