No tire issues at all here at 7,300 despite not having the tires rotated which makes me wonder if some of the issue is "dry turning".. Though only ~300 pounds heavier than a typical Prius, the LEAF is over 50% heavier (~1,200 pounds) than my previous car (an '01 Kia Rio). In other words, this is no lightweight vehicle. All that weight on the tires can easily wear down tires and lead to "chunking" if you're not consistent about only cranking the wheel while the car is in motion. Then again, I went through the Firestone recall routine so I can certainly understand that there might be a bad batch of tires out there.
Really wishing that my two-wheeled vehicles had TPMSs; I've run over more nails and screws on my motorcycle and scooter than I'd care to remember, and a TPMS would have helped me avoid the problem of realizing I couldn't steer very well until I was partway through the corner...