With the release of 11.0.5, the class ensembles from MoP Remix are now useable by any character with a matching armor type!
When October's Trading Post catalogue was announced, Blizzard also revealed that in November, we would see the return of the Class Ensemble sets not only for their original classes, but for all classes of that same armor type. This means that all plate wearers can interchangeably use the Death Knight, Paladin, and Warrior sets, and likewise for the other three armor types.
One glaring absence, however, was the removal of restrictions from the matching recolors that players were able to obtain from MoP Remix over the summer prior to the launch of The War Within. Thankfully, Blizzard hotfixed this shortly after 11.0.5's release, and the recolored ensembles are now also available!
This applies not only to the armor sets, but to the weapons as well.
For those who need a refresher on what these sets looked like, you can find a link to the ensembles below.