Couple suggestions how you could improve your setup to get better result. Change subdivide mode to variable curvature, it will allow you to have more finely subdivided edges without blowing up polycount. Use several noise modifiers, first one with large scale and strength and each subsequent with smaller values and don't forget to change seed. Never use default seed! If you add chamfer modifier, you then can use some selection modifier to select only edge vertices based on curvature. I used tySelect for that, but you can use data channel. After some tweaking of the settings, you should be able to achieve pretty convincing results.
