PlantUML provides such extra "perusation" to the layout. It works often.
But PlantUML's documentation is too scattered that it's hard to know how much it supports.
Overall, to me, PlantUML is one of the more promising trade-off for userability and sophistication.
I wonder if we could pool our resource together to help one reach to more userability.
Often I use invisible subgraphs to accomplish this sort of thing in GraphViz, but the markup for doing so is complicated and non-obvious.