I had cloth heated seats in my mk5 and they worked great, about 1-2 minutes into the journey and you feel them working. Wow they were good - so much so i looked for heated seats on used mk6's before i bought a mk6. Rare fitted option in the UK.
Eventually found a mk6 with leather, a gt model. But my mk6 leather heated seats take a lot longer to get hot - like a good 5-10 minutes to feel anything. Very much different.
On the heating element i would expect to see some sort of controller to be able to vary the heating. A pulse width modulation of some sort, which would suggest there may be an adjustment somewhere.
To check the pwm output a dvm may actually work. Closer to full battery voltage on max heat would suggest the controller is putting all the power it can deliver to the heating elements.
Perhaps VW had law suits about mk4/5 so they made them less powerful on mk6?
In a similar subject - I tried to get the memory to work on the seats to remember the last setting, but my module does not update via VCDS. My mk6 is an early 2009 UK model.