World Quests tell you exactly which slot.
It is more useful than the random LFR drop.
World Quests is FOTM.
I don't see why anyone wants to run LFR 2nd time.
Edit: LFR cannot even do the quest (Essence of Power).
It is out of favorite.
It is really sad that Blizzard doesn't balance the reward.
Instead, it "forces" us to do this or that content.
I bet the hardcore are not happy now because the enchant and pot are so expensive.