Just got my 2nd from level 9(was a 2 chest run). Done about 60-80 in total(different levels).
You really can't predict. To be honest, before I got mine, I lost all hope(i did plenty of dungeon). Was actually farming for another dungeon item.
If you really want to optimize(and believe me, you get it in the end):
1)Regular Mythic.
2)Regular Raiding(all you have access to including LFR, Normal, HC and especially Mythic).
3)Daily chest.
4)Then it's all about mythic keystone farming. Higher level is better chance. Try to perfect specific dungeons over and over(especially those that actually gives you other gear). And if you can tank, that makes it even better experience for everyone.
Most importantly - don't stress about it. If you are doing keystone, purpose is to perfect your experience everytime. It makes it so much more fun.
If you have access to Tank/Healer spec, use it for faster groups. Just set your loot-spec as whatever your main spec is.
Last edited by mmocd6fe3ee806; 2016-11-12 at 05:43 PM.