USKP v1.2.2 - (2012-10-05): "Idgrod the Younger is no longer incorrectly set as Morthal's Housecarl and is no longer essential."
v4.0.6 (2017-02-05) [SSE 1.4.2]: "Dorian is incorrectly set up as a static level NPC capping at level 251 due to what appears to be someone typing the proper range into the wrong boxes. He is also marked essential but has no purpose in being so. (Bug #21736)"
If Rolff Stone-Fist being essential for seemingly no reason is not a bug, then Idgrod and Dorian being essential should not be considered bugs either. The other changes to them mentioned in the log are bug fixes of course.