Alright Cabal players.. I need some help.

I have a total of 20 hours grinding on Death Knights, Wraiths & beetles... so no AXP no EXP looking for this Epp of Proof +4 Form Card #75.

Can anyone point me in a better direction?? Does anyone know the most common area that this drops?

EST... you may want to consider increasing the drop rate for the proofs or add to cash shop. Makes no sense to make a 168 WA graind 20 hrs... FOR NOTHING!

There is only 1 in AH and it is for 350 mil O_O

Thanks iin advance alll...