There's quite a lot of NPC's that appear in solo duties for various class quest's, as well as for the MSQ (I think, could be remembering wrong tho), that should appear in the party list IMO. For instance another is the marauder NPC you have to heal in the Scholar lvl 30-50 quest's.

You can get around this by selecting the NPC and using the option "focus target" on them - this will ensure you will always have them showing up on your HUD, while still being able to target enemies and friendly NPC's at the same time.

However this work-around only works if there is 1 NPC you need/want to keep track of, as you can only focus one target at a time. So if you have multiple NPC's, then your stuck with only having 1 focus and manually having to check the other's - as I've not done the WHM lvl 52 quest I don't know how many NPC's are involved.