I've handled a few jobs like this in the past. We have several Rimage Producer 7100s that we use mainly for duplication, but they can be run "backwards" to bulk read/copy data from DVDs as well. We have loaded as many as 600 DVDs at a time and walked away for a few days and it does the rest. It's expensive hardware to buy if you were just buying it for this task, but it's pretty handy to have.
Other than something very specific like that, I'm not sure of any better way to do it, but using a dedicated copy utility other than dragging-and-dropping in finder would help so that the entire process doesn't abort due to a single error.