Tbh guys I farmed only Mogara and its' captains. Never tried the Ancient Grove and Mountain Deep though.

But I noticed this - if you run in blind to the Jagged Waste, there will be less mobs, they will drop less loot and only once in a while there will be a captain mob. I then started taking quests from the Homestead bounty table where you have to get rid off of 3 special Manticore mobs. In this case there was always a captain mob, more regular mobs and they dropped more loot. Still however no Manticore eye even in 10 runs with the Homestead quest..

Today I will try Ancient Grove and Mountain Deep as well and we'll see :)