yeah, simetry is cleary what is killing the trees here. but adding the small brances you did kill part of the problem, but the treetop still needs to be broken to asimetrical shape.
the pine as Bissle said, has the same exact problem. its nature, its no suposed to be simetrical. its suposed to be a bit more unexpected.
you also might want to shade the sides a bit darker and had a bit of a highlight down the pinetree to give it a round shape. right now it looks flat, like a cut out, because you have the same lighting values on the whole area
Kaz