Here are the Weekly Nerub-ar Palace tuning changes which includes new abilities and Private Auras!
In the best news of for Nerub-ar Palace for Private Auras:
This ability was projected to be worse than Neltharion's Volcanic Heart with a total of 8 players getting a debuff (+3 of Neltharion) and only having 6 seconds to figure out what to do with it (-1 second of Neltharion). Thankfully, it's no longer a Private Aura, but it will still likely be Weakaured.
Here's an example of testing from Heroic when it was Private Aura'ed and there were only 4 debuffs.
There are some new Private Auras, but none of these worry me as these don't see as bad as some of the others currently.
In the case of Phase Blades, I do actually think Private Aura'ing this ability makes this boss much better. Getting told exactly what number you were right away does make the mechanic kind of lame. This is one circumstance where I agree with the Private Aura'ing of this mechanic.