Yeah, this is normal for the AD831. It has a supply current of 100 mA nominal on a 9V supply, this is almost 1Watt of power it must dissipate from the PLCC package, which has no ground paddle to act as an efficient heat sink.
You may want to try putting thermal paste between the bottom of the DUT and the board. This may conduct some of that heat away from the board to the PC board better.
Hope this helps,
Joel