#0 - Jan. 1, 1970, midnight
Azerite essence in proving ground
#1 - May 22, 2019, 8:50 p.m.
Yes we can view all the rank 3 essences in proving ground, however we cannot test them - “You must be in a rest area to change essences.” And the rank 3 essences are not available outside when we get out of proving ground.
#3 - May 22, 2019, 11:25 p.m.
We applied a hotfix to the PTR a few minutes ago that should allow you to change talents and Essences in the Proving Grounds.
Additionally, Tome of the Quiet Mind & Codex of the Quiet Mind should let you swap Essences around.