Dupes. Many times analytics returns a row per unique URL with parameters (100 page views for /blog?page=1, 20 page views for /blog?page=2, etc). Ordinarily content analysis is most useful at the level of listing pages as opposed to exactly what depth of pagination (so an inventory would just have a line for /blog). So when merging pageviews, these should be summed if there are multiple pagination urls for the same conceptual page.
Missing values. If an analytics tool indicates no value for pageviews for a URL, in most cases this can be considered as a 0 for the value (no pageviews). On the other hand, it may be an indication that the analytics package is misconfigued.
Chimera imports data from a variety of analytics vendors. It also correctly deals with URLs that are duplicate from the content analysis perspective (such as those with campaign IDs).