So, as of today all LibreOffice (3.5 onwards) text rendering under X goes through cairo. This was already the case in practice for horizontal text for quite a while, the additional change is that its true for vertical text as well now.
before
after
Yes, I know it’s still rather sub-optimal. The current implementation is basically intended to be bug-for-bug compatible for now, though I couldn’t resist improving the positioning of 0x30FC.
Test-case at http://cgit.freedesktop.org/libreoffice/core/tree/qadevOOo/testdocs/vertical-testcase.odt