Im trying to clean up an ecommerce website with about 2000 products and 1,800,000 pages indexed by Google. Site sells products that are often searched by category, designer, size, weight etc. so some of the pages have all these attributes in the url and look like this: site.com/category-designer-size-weight.aspx and that is the reason behind 1,800,000 pages indexed by google.
Although these pages are helpful to users imo, because they can bookmark or email these pages, I believe they hurt search engine ranking by creating duplicate content and taking away the juice from the product pages.
So my question is how to better deal with this problem
1) Remove URL redirect for these pages only, and let google know they are dynamic Ex: site.com/category.aspx?narrowdesigner-size-weight
2) add nofollow to this page
3) set priority in the sitemap
any other suggestions would be appreciated.