Primal Ancient Legendary items drop rate 1/400 understand that but very likely can not use on build due to want to use stats exceptional drops.
My suggestion to Kanai’s Cube add Reforge Primal Ancient Legendary items option for reforge.
Requested materials can arrange for per try;
Bounties x 25 (each)
Forgetten soul 250 and i think nobody’s objection this spending amount.