Mark,
The chair is more like 2000 to 2500V rather than 25kV. The document I quoted did indeed show that in one case the prisoner's body resistance dropped as low as 133 ohms. (This was Fla. before they pulled the plug.)
On the defib issue, a medical drama show (British) the other night did actually quote 360 joules for the second and third attempts (they didn't mention the energy on the first).
