How about using more modular assets? Perhaps, using modular assets would save time and it would make better quality rocks. I have a nice tutorial website which could be helpful for you. http://www.philipk.net/tutorials/modular_rocks/modular_rocks.html
In terms of organic sub-d vs. hardsurface there are many differences, but perhaps the more important workflow difference with this specific enviro is the one that arises out of your choice to use unique-prop/modular-instances or tiled texture sets and trims, because that will determine most of your workflow and how much…