You'd probably do more harm than good if you just dropped the 700 pages that are copied. Google hate's to see massive jumps up or down in large amounts of your pages. Makes them think something is amiss
Your pages are only hurting you, if you get a manual penalty which will show up in your webmaster tools, so if you want to get rid of them, do so slowly and make sure that they aren't picking up search terms already. Again google gives us all the tools we need to see what needs help and improvement on our sites with GA and the webmaster tools, we just have to use them
Good luck