Did not get Mecha Perfection Turbo rank4 from Hertz Locker Hard mode

In order to be eligible to loot the rank 4 Vision of Perfection essence, you must already own the rank 3 essence. Completing the hard mode achievement Hertz Locker before you have received rank 3 Vision of Perfection will not drop the 4th rank.

Once rank 3 is obtained, you should be able to visit Prince Erazmin in Rustbolt to obtain the Rank 4 essence without having to complete Hard Mode again.