Valid points. Especially the central tree is very much a solitaire. Still, you could put them a bit more apart than in your example. LB's example works for me, as does this one:
Actually, I like this more. Your trees look like a young forest, while this looks like an older forest, where some of the trees died, while the others continued to develop, growing bigger canopies in the space that got freed up, leaving space between the trees where once the other trees where, and young trees no longer get a chance to develop.
Relatively young and not so developed trees are often used to make forests, as, while such trees individually are not that great bonsai, you still can get good results. Doesn't mean you cannot use more developed trees. On the contrary, I'd say.