Hi Kyle,
In my experience, one of the reasons why slicers don't always tend to work as expected is because of the fact that some slicers may be located in Group Boxes, and whichever component does not fall under the purview of that group box, the slicer may not work with them. Also, I do agree with you, I've noticed that sometimes the Data in HTML box appears, sometimes it doesn't
In fact, I'm interested to know if you have a plan to modify the OOTB report to allign with what you had earlier in R11.