The Diablo 3: Reaper of Souls achievement Sightseeing says to "complete all of the following events in Westmarch." There are sixteen events to complete in Westmarch Commons and Westmarch Heights.
The final piece of the puzzle for me is Tollifer's Last Stand. According to this post on Blizzard's forums it is in Westmarch Commons. This video shows it being completed, but does not go into much detail.
I have performed a full clear of Westmarch Commons many times both in Adventure Mode and in Campaign Mode. I have seen every other event multiple times by now, but not this one. As the video advises I have been very diligent to keep my eyes peeled for doorways with the sparkly body and on the minimap for the dot. Nothing.
How do I complete this achievement? Do I need to be on a certain mode? Is it really super rare, or am I the victim of the RNG?