http://www-nz.cricket.org/link_to_database/ARCHIVE/ICCODIC/
Those are the official ICC ratings, based on the last three years. It makes no sense for Kenya to be in the top 8 based on 3 wins, (two of which were against Zimbabwe and Bangladesh). They are, however, above Bangladesh now.
I don't think there's any sport that bases it's ratings solely on the world cup, simply because it's a one off event (eg. Sth Korea definitely aren't #4 in the world at Soccer).
Lots of people have trouble with the ICC ratings, but I think the fact that they're based over such a long time period (which makes senes in cricket) it's easy to forget the recent results.
NZ has always played badly overseas, especially in ODIs. I think we've won about 3 or 4 series overseas ever (including against Zimbabwe). If you look at the link above, you can also see there's not much between #8 and #3