The latest expansion Holy Fury is quite good. I tend to play CK II once a year around this time and I think they have done a pretty impressive job of putting out a substantive DLC compared to some of the prior ones.
The shattered worlds option is one of those changes where you can't believe it didn't exist sooner. Customizing your religion when reforming is another nice feature. Definitely worth a look for those out there who have put lots of time into this previously.