I think there is a bug now. We spent over 200000 glory (plus glory 10k chests), 1400 gem chestss, 150000 seals, 50 VIP keys and… NONE of 4 members could get it.
I saw on FB community site that people put a lot of resources and nothing.
Even with 0,01% - 0,11% ratio drop we should get 1-2.
I got all last 10 mythics without any problem.