followup, found a basic diagram of turbine PVT transitions here
http://www.skybrary.aero/bookshelf/books/1621.pdf
This turbine is designed for a fair bit of back pressure however, so it can drive the compressor, though the gasses feed a convergent nozzle downstream. I assume the top line is temp, the middle is pressure and the inverted V is velocity. So while the vane stage doesn't do any compressing (temperature stays the same), the blade stage does some expansion, and hence the temperature drop across the blade?
So, does it stand to reason that if this turbine magically did not need vanes that temperature would drop faster than pressure?
(reading about Rankine and Carnot Cycle now)