Yes. Absolutely correct. You should never index tag pages. These may be targeted but are of low quality with not much quality content. Moreover, they may have more keyword density than what you should have for a page to rank.

I have an article on that here. An extension for firefox called Dust-Me selectors can help you identify unused CSS on multiple pages. It tracks all the pages you visit of a website and tracks classes and ids which were never used. Moreover, you can also give it a sitemap and it will figure out the CSS which was never used.