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.
Note that lower level fields may sometimes be needed to compute more useful fields. Also, sometimes the higher level fields may be more difficult to compute, so they are not always worth it.
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).