Why is the Solar separate instance from Waking Sands / Rising Stone?

[Iscah]

It's used as a cutscene trigger point as well sometimes, which is probably why they've kept doing it even when the entire zone is private.

[InkB]

It's used as a cutscene trigger point as well sometimes, which is probably why they've kept doing it even when the entire zone is private.

Most likely this. There are also LOT of changes inside THAT room specifically. NPCs change, cutscenes trigger in and out of it. Quests appear after certain changes, they didnt want npcs to just appear out of thin air after you walk thro a door.

Well - they have new systems in place atm that help with that. We've seen that they can do this in SHB content and some late SB content (if I recall).

However I suppose its old PS3-way of handling things and theres kinda no reason to change it "if it works"