Unsealed Chest drop from LK 25N with tabard of the lightbringer

I killed LK last 30 days few times with shadowmourne and Unsealed Chest with Tabard of The lightbringer,
Arthas' Training Sword, Badge of the Silver Hand, Blood of Sylvanas, Jaina's Locket, Alexandros' Soul Shard and Reins of the Crimson Deathcharger doesnt drop for me, probably becouse i bough the mount long time ago, or for some other reason that i dont know. I made few tickets and received only copy/paste answers ""we cant help you with your isue"" , so if someone know how to obtain the chest plase help me.

and i had the sam problem