Cannot find anything in Desert of the Lost

hi,
I entered to the desert of the lost map (with scroll) 5 or 6 times (1 with a group).
Each time I survived 2-4 waves.
got 0 (zero/nothing/null) "Essence Water".
is it normal? how can I made event progress with no drop?
the other group member got around 60 essence at this time.
even tried to go to white map, clean it all but still, not even one essence.

Do I have a very bad luck or this is how the even goes?
(this is my second month in the game so maybe this is stupide Q)

 

After each finished wave (Sanmdstorm) certain number of chests spawn in the central part of the map.
Open them up!
The more waves you finish the more chests you open. The more chests you open the more Essence Water you get.
The drop stack amount is difficulty dependent.

 

yea, I read about it.
I saw only 1 chest and got 3 essence from it....