Heydarian, great to see you here.
This is a complex question. The answer of what to index and what to not index varies from situation to situation.
Let me give you examples and a little history for two sites...
**BLOG A ** (an industry news filter, kinda like Metafilter for an industry)
The site that I spend most of my time on has a blog that receives very skimpy posts. "You gotta see this widget". "This widget is really cool". "Acme invents a new green widget". Three years ago, I had post pages, category pages and a home page that all received lots of traffic. Then, after Panda, those skimpy post pages did not perform well and actually damaged the rankings for the entire site - because I had thousands of them. So, I noindexed all of the post pages and even deleted thousands of them a couple times per year because they were mostly "newsy" content. The category pages and homepage still received lots of traffic and the rankings for the rest of the site recovered nicely.
Then, I think google started looking at category pages that link to skimpy content pages and they started performing poorly. So, I changed the blog format to eliminate the post pages and the category pages. Now there is only a big homepage and pagination pages. This blog still is very successful because lots of people continue to visit it directly and subscribe to the feed - but I intentionally abandoned the post pages and category pages because Google has changed.
BLOG B (a product blog for a retail website)
On this blog the posts are detailed product reviews, detailed descriptions of how to do something, detailed quashes of misconceptions, etc. Each post has several photos and 500 to 2000 words. At first I was using about ten category pages, but after a couple years they still were not getting much traffic. Other pages of my site (not on the blog) competed with them and performed more strongly. So, I deleted the category pages from the blog, HOWEVER, I began to generously link to the topic pages on other parts of the website. The results have been positive.
So, the bottom line. I think that you have to look at many things:
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Are your category pages pulling in traffic? If not, delete them, don't just noindex them unless lots of people are reading them. They are power sinks if you still have them on your site IMO.
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Do you have superior pages on your site for the same topic? If you do, then give them your attention and promote them on your blog posts.
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How does google treat pages like yours?
Then you gotta place your bets on a strategy. Hope that it works. Keep watching the analytics.
Good luck.