So there are three super unique bosses that are optimized to drop the crystals you are looking for.
Cold crow, in the cave in cold plains I think.
Ancient Kaa, he only spawns in one of the tombs.
The boss down in flayer dungeon.
The runs start getting fast when you learn where to look on the map to find them, you can tell just by looking at how a certain part of the map is snapped (like farming lower kurhast chests).
You should be able to fulfill your crystal needs there.
If you have more issues or things you would like to bring up and share, the subreddit is probably the best place for that.
Another great place for information is the wiki but you seem to already know that hence the socket recipe.
Good luck and hope you give it another try!
Amek206
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