World of Goo (90%), Machinarium(90%-95%) and the PC Gaming Alliance (90% for high end titles) have all claimed piracy rates of 90% or above.
Also there seems to be a gap in your reasoning, going DRM free didn't cause the overload on their server, unless you're claiming that going DRM free caused people to pirate it. The huge pile of (previously) DRMed media currently being pirated would beg to differ with you. They did use accounts (or a code per game), so the pirates were unable to log in to the server, but the fact that they were trying to is what was causing the problems (from the update at the end of the article). If they'd had DRM, it would have been cracked, people would have pirated the game, tried to contact the servers and they still would have fallen over.
If they had implemented DRM for multiplayer access to the server, they would not have failed. Attempting to contact a server and being told 'No' isn't the same as having a connected player. I'm talking Steamworks-style DRM here, which is online logon for multiplayer, requiring authentication against the server and username / password tied to purchase. It works well for that purpose.
If they had used it, those early reviews would not have suffered, and their servers would not have been overloaded short of a DDoS.
Also there seems to be a gap in your reasoning, going DRM free didn't cause the overload on their server, unless you're claiming that going DRM free caused people to pirate it. The huge pile of (previously) DRMed media currently being pirated would beg to differ with you. They did use accounts (or a code per game), so the pirates were unable to log in to the server, but the fact that they were trying to is what was causing the problems (from the update at the end of the article). If they'd had DRM, it would have been cracked, people would have pirated the game, tried to contact the servers and they still would have fallen over.