I wasn't expecting much while looking for assorted Lutheran records from Werther. But I recently found a detailed marriage record for Ferdinand Friedrich HOLZ and Anna Katharina Ilsabein DEPPERMANN which noted who their fathers were, where they lived and when they were born. This may not seem like a big deal, but glancing through the IGI you won't be able to determine when the bride and groom were baptized, despite thousands of Werther records having been indexed.
It looks like the missing baptisms may be the result of an incomplete index. I noticed this when I started to find "new" VOSSIEK baptisms while going through every page. I'm not going to spend time analyzing how many records were not indexed, but it's worth noting that I found the VOSSIEK baptisms in the section for those that lived in the Werther parish (kirchspiel), outside of the city (stadt).
So, within the next few days I'll be back at the library trying to find the HOLZ and DEPPERMANN baptisms. Hopefully, details will lead to the names of their mothers, which would then lead to marriage records. Even without the baptisms, though, the dates of birth listed in the HOLZ-DEPPERMANN marriage record shows that they were older than that was indicated in their passenger list entries.
As far as the other names I'm researching in Werther -- KINDERMANN, SCHIERBAUM and WURSTEBROCK -- I did find a couple of marriage records, but haven't finished looking for deaths/burials.