We'd found out after posting that the Rogue in that group ended up being a rename (DH name -> Rogue name) which caused the data to be overloaded like that. This lead me to believe that anywhere where the actual role is indicated as Tank, but the person wasn't really a tank, that this is actually a rename.
The runs I posted where it shows 4 actual DPS roles though are different, and I am wondering if this could be a respec at the end of the instance by the Druid healer:
https://raider.io/mythic-plus/runs/4...halls-of-valor -- or Blizzard is marking them as DPS when they aren't (we get this role field directly from Blizzard).