I think for most folks, the only type of retouching that is worth outsourcing is portrait work. You can provide a reference image and then someone can clone that look. Insofar as it becomes grunt work, it makes sense to outsource.
Me, I don't even repeat myself when doing that. Every image is unique, and requires at least some attention. But I don't do fashion, or commercial, or editorial. And if I need to clone settings, it's usuallly the case I'm staying in LR and can simpley copy/paste settings, then crop and minimally fine tune the exposure.