For example, although this is possible for Parsoid to parse the [[Dolphin]] article:
http://parsoid-lb.eqiad.wikimedia.org/enwiki/Dolphin

... if I try to get the PDF version, OCG dies with error:
<<
Generation of the document file has failed.
Status: Rendering process died with non zero code: 1
Return to Dolphin

Version: unspecified
Severity: critical