Haven't read through all the thread yet, so please forgive me if this already has been mentioned:
There should be something done about either the Barbs (what I would like less) or the tundra.
Happened now for the second time to me that I came up just one tile north (or south in the first case) of a large tundra area. So - as there was just plain grass, I walked some tiles until I founded my capital. Now, of course the victory point location (seems to be standard) was adjacent to the tundra. As the tundra area was really big, I was never able to secure that victory location, as the Barbs constantly killed off my units.
And now it comes! As the AI seems to have some kind of non-agression pact with the Barbs, finally one of them settled just next to it, regardless of the poor environment. Pooof, victory location gone :-(
My idea would be to make tundra 'unsettable', but give it 2 grass/1 shield. The other option would be to get rid of this misconcepted type of environment (misconcepted in C3C, not in RaR!)