In Icemist Village (Dragonblight) there are mobs called Anub'ar Cultist, which cast selfbuff named "Zeal" which increases cast speed by 20%. The debuff is spellstealable, therefore you can spellsteal it (yeah!), get summoned to raid and have free 20% haste for two minutes of fight.
Also in Pit of Narjun there's a named humanoid mob with same spell.