Kind of hard say the drop rate although don't seems that punishing to many.
I do say I been quite lucky, on a 3 hour playtime,
Day 1 I get 0. Day 2 got 4, day 3 got 7. So now total 11. Today go home farm remaining 5 dungeon.
As for crafted item they were abt 100 k for hq finished ones here so got all 8 easy :x
Friends that do with me some have 3 after 3 days, sone 7 to 12.

Sastasha took my friend 1 shot, while me took 11 tries. So is very random, pray your luck