Dave, you mentioned in the tear down the element had three connections and one for the thermocouple!
One of the connections on the element will be the tip grounding, the other two the supply feed to the element - from what I read somewhere on the JBC site was that the thermocouple was in the actual element.
You referred the current shunt as a four terminal device... the resistor is a 0.005 Ohm 5W 1% they are printed as 5L0F or 5LO see pdf
http://www.vishay.com/docs/30327/wslmarking.pdf the two finer connections will be a tapping across the resistor to monitor the voltage across it, this obviously monitors the heating current.
I was seriously going to get a Weller WD1000 or WT1012 until I read about other Weller's models failing in warranty!! I then came across the JBC CD-2BD this uses the T245-A while the JBC CD-2SD uses the T210-A .... the irons are both interchangeable, the station will also take the matching tweezers.
I was nearly 'had' by buying a Atten (Tenma) soldering station...... I learned many people had problems with the tip loosing heat, imagine using solder wick and that happened.
It would be interesting to hear how the temperature response is on the JBC. Thank you for the reviews and tear downs.
Dave