indyank - 5:46 am on Dec 29, 2012 (gmt 0)

In that case a large majority of the 90,000 backlinks will come from pages with mostly unrelated content, and all links to the same page on your site will have the same anchor text.

yes, there are two issues there.

1) links from unrelated content.
2) site-wide or category-wide links from their end.

Both are not useful anymore.

The other issue is a few domains contributing to your link profile. If your content is too good as you suggest, then Google algos would like to see links from more domains than a few, as in your case.