I doubt that last part. Because LFR has a chance to give anyone in the raid any loot, while in normal/heroic mode they would have to assign who gets the essences this week. While I think all raids should get it, that would be a pretty stupid bias towards LFR and it's loot set up.
---------- Post added 2013-06-17 at 08:42 PM ----------
Doesn't someone who clears heroics have a better chance? They can still run LFR to get the items, and then run heroic afterwards. That's double the opportunity.