What i would suggest for the barrens,is instead of using large shrubs, use lots of little shrubs grouped together nearer to rocks and trees a little bit more, and then maybe have some larger shrubs out in the open like you have them.
And for the swamp, that fog just looks plain bad, use maybe a dark green fog for the swamp and then use the eerie fog doodad from the UTM around rocks and trees. Also i personally hate the leaves that were used for those willow trees (not your fault) its just a very poor way of making them in my opinion. You should look for the Swamp tree's in the UTM as well under -Enviornment- The ones with the roots above ground, possibly you could put rocks underneath those or just lower them a bit farther into the ground.
Overall i'd say more rocks that are a little bit more grouped together and smoother cliffs (Right side of the barrens shot) you can also use those rocks you have on top of those cliffs to put on the cliffs (at the base place larger rocks that go into smaller rocks as you hit the summit) and then place rocks on the face of the cliff, but not to many!