You realise him signing off on everything is actually just your imagination of how Blizzard works. It also does not mean that he actually looked everything through, mostly because he wouldn't have time for anything, nor does it mean that he can accurately predict how these systems are ultimately going to work out.
No, you're simply assuming that all fault can somehow be traced back to him without being able to actually provide any evidence other than him being at the top of the hierarchy.
I'm sure if you have any employees, you wouldn't accept the blame for everything they do, either. Even if you did sign off on it.