I haven't used the game much but my impression is that it seems to match my subjective experience of my state pretty well.
GSR seems to be rather unstable and I don't think it's necessarily a good indicator. I have another GSR device that seems almost useless, so your experience isn't unique. Another problem with GSR is that it depends on other factors, like the ambient temperature--if it's hot, you sweat, and that increases the moisture on your skin. Your physical state, whether you've recently been active, etc have similar affects. Those other variables are why you have to sit with the WildDivine hardware attached for awhile (a minute, I think) before starting, so it can calibrate for your current conditions.
The WildDivine gear also measures heart rate variability and breathing, which may account for its greater seeming stability than plain GSR devices. HRV is probably a more reliable indicator than GSR (my opinion only, based on minimal actual technical information). I don't know for sure how it measures breathing, since it doesn't have a chest sensor--probably deduces it from the heart rate variability.
There have been a couple other threads over the last couple years about WildDivine, but I don't recall any discussion of the actual hardware. One thread is currently on page 1 of this forum, and here's another from the "Astrology, Spirituality, and Alternative Healing" group:
http://www.democraticunderground.com/discuss/duboard.php?az=show_topic&forum=245&topic_id=8009I know there was at least one other thread somewhere about it, but I can't find it.