I have about 5 primal so far. Two of them came from Kadala. Two were sent as Gifts in the mail. I also sent out 3 gifts that contained Primals . I have only found 1 Primal in rifts and have probably done over 100 . Of the 5 that I have I only have one that I use ( Cage of the Hellborn ) and the others not useful for my build.
Seems to me that receiving gifts from friends and gambling with Kadala is more efficient then rifts and bounties. Have had no luck upgrading rates. Have done probably 300 with no luck
Find primal all the time. I stopped counting. Got a Dayntee and trag head primal (im using inarius) for my Necro . Everything else in the Forge. Usually in 4 man group, fast finish on regular and Greater rifts like 4 min.
When you do find primal, you have to leave and find new 4man party. I've played for 4 hours, same party, find 1 primal.
But find new game after 3 or 4 runs and keep switching between GR and regular. Primals so often i don't even know I have them till my inventory is full. a whole bunch of useless, non set, non specific garbage primals I cannot use. I almost rather not find anything. Get super excited when you see the red border, same time disappointed when it's no where near what I can use. My heart cant take it.