You mean Path tracing. Ray tracing is the standard method and indeed has a flatter light in veggies. Your PT render comes out really well, very much improved and a great scene altogether. The cloud is gone, great; photoshop or simple shape?
Two more things I'd like to suggest. The river is part of the landscape, you said, and does have a problem. Is it that flattish overall that you could use it mask to lower it into the ground and add a plane/sphere as real water instead of just the water shader? That would get rid of the water being higher than the shores, which is visible in front. Too bad actually, as further down the river it looks just right. Perhaps a local soft sss can repair the displacement so to speak, smooth it a bit there (by surface shader after main displacement).
Another thing would be to add the internal grass pop to give the open ground just a little softness. Subtle green/brown color variation (through transform to world in the object), have it's object sunk a little in (-0.2) reduce X and Z to 0.7 and make it 0.6 high or so. To make a gradient use a distance shader to fade the grass out to distance, and try to get the ground color as grass color, so it won't stand out too much.
