Oh really?
For each item that drops in PL, the game has to make 2 rolls. 1st, it rolls a player to receive an item, then it rolls what item to give them. Now, not every item is on the loot table for every player. Using Sylvanas and Edge of night as an example, is only on the rogue loot table. but the ring is on the loot table for every player in the raid.
For Edge of night to drop, the game 1st has to roll that a rogue is going to get the drop (often a 1 or 2 out of 20 chance), then It has to roll edge of night out of the 4 items that a rogue can get (belt, chest, ring, dagger). If we assume 2 rogues, Edge of Night has about a 1/40 or 2.5% chance to drop. with 1 rogue, the drop rate is would be 1.25% or 1/80.
For the ring to drop, the 1st roll almost doesn’t matter. Everyone is able to loot the ring. Average size of the sylvanas loot table across all specs is approximately 4 (2 cloth, 1 agi dagger, 1 bow, 1 hunter cape, 2 plate, 2 leather, 1 mail, ring, str trinket, and shield). Running with this, the ring has about a 25% chance to drop. If I add up the loot table for the exact comp my guild killed sylv with, the ring has just over a 30% chance to drop.
PL makes certain items artificially rarer drops than ML does (under ML, the drop rate for both items should be 1/12).