The language packs seem to have changed in Win10 1607.
How are they supposed to be named in order for MDT to install as part of a task sequence?
*edit*
It looks like the cab file still needs to be in a folder titled the same as the language (de-de). The names of the cab files have changed: "Microsoft-Windows-Client-Language-Pack_x64_de-de.cab"
This file works for Win10 1607 but will not work for previous versions (1511 or 1602).