Is mythic leather supposed to be super hard to obtain?  Need it to upgrade Alchemy III, where I hope can then craft it, but collecting in the first place is proving rough.  Two jungle dungeons, and a mere 7 leather.  Just bad luck on my part?

In my experience, it's kinda random. You can get those from chests/caches, but the most reliable way is to grind jungle dungeons, as most bosses give it. The amount is low though...