I figured out the problem with last nights cake. It wasn't the combination of flours that caused the bread-dough like consistency. It was the Xanthan Gum. After perusing through my GF baking book, I realize that most cakes and light pastries call for very little XG. While breads and crusts call for a bit more.
Due to my uncertainties about the flour mix, I used 2 tspns - and apparently, that was way too much. I'll remember that for next time!!!