Short version:

  1. Edit View Title Family
  2. Turn on the reference planes in the Visibility / Graphic Overrides, select all three items. 
  3. Rotate these items opposite of what you think to offset the rotation of the view. So if you are rotating the view on the sheet 90 degrees counterclockwise, you have to create a view title with these three items rotated 90 degrees Clockwise. 
  4. uncheck “Keep Readable” under the instance properties of the text labels or Revit will try to make the text read up the page, not down.
  5. Save View Title family and apply it to Viewport Type in project

Long / original version, this idea and steps above taken from this post by IMAGINiT:
View Titles for Views Rotated on the Sheet – IMAGINiT Building Solutions Blog

Firstly, consolidate your Viewport Types by using Select All Instances – In Current Project and switching them to the Types you want to keep.

Then, change a Viewport to one you want to delete, and use Snoop Current Selection (RevitLookup).  You can drill down to find the ElementID of the Viewport Type Definition:

Ok, with this in hand:

  1. Change the Viewport back to one you want to “keep”
  2. Select by ID – use the ID you found above
  3. Press Delete on the keyboard (if any viewports still use this definition, Revit will prompt you that deleting this Viewport Type could cause problems etc). 
  4. Rinse and repeat
Keep in mind that some Viewport Types are “special” / built-in, you will not be able to delete them all…