The daily quests from Wind Trader Zhareem and from Nether-Stalker Mah'duun are marked unobtainable.

I believe they were once removed from the game but are currently available again. The Wowhead comments on each of the quests confirms that they are again available in-game even though Wowhead implies the opposite.

Zhareem:

• WANTED: Nazan's Riding Crop
• WANTED: Keli'dan's Feathered Stave
• WANTED: Bladefist's Seal
• WANTED: The Heart of Quagmirran
• WANTED: A Black Stalker Egg
• WANTED: The Warlord's Treatise
• WANTED: The Headfeathers of Ikiss
• WANTED: Shaffar's Wondrous Pendant
• WANTED: The Exarch's Soul Gem
• WANTED: Murmur's Whisper
• WANTED: The Epoch Hunter's Head
• WANTED: Aeonus's Hourglass
• WANTED: A Warp Splinter Clipping
• WANTED: Pathaleon's Projector
• WANTED: The Scroll of Skyriss
• WANTED: The Signet Ring of Prince Kael'thas

Mah'duun:

• WANTED: Shattered Hand Centurions
• WANTED: Coilfang Myrmidons
• WANTED: Malicious Instructors
• WANTED: Rift Lords
• WANTED: Sunseeker Channelers
• WANTED: Tempest-Forge Destroyers
• WANTED: Arcatraz Sentinels
• WANTED: Sisters of Torment