The continuity issues with Dark Mirror
apply to the Federation timeline as well. For instance, in the novel, the events of "Mirror, Mirror" are classified and need-to-know only, but in "Crossover," Bashir says he learned about them at the Academy. Also, DM says that the laws of physics would cause devastation on a galactic scale if any large amount of matter from one timeline stays too long in another, which is inconsistent with "In a Mirror, Darkly" vis-a-vis the Defiant
, as well as the 2009 movie vis-a-vis the Narada
, and probably a few other things as well (including my interpretation in Forgotten History
of the origins of Miri's Earth).