And why isn't the fresh blood of Mannoroth hopping up Grom and his warriors like super steroids counted as a magical effect? He even temporarily turns into a red chaos orc and starts dealing
chaos damage in the game.
Gorehowl is
also a magical weapon. Basically every semi-important weapon in the Warcraft-universe is magically imbued in one way or another, including Rexxar's axes, the swords of Lothar, pre-DK Arthas' Hammer, Turalyon's blade, the Axe of Cenarius, Doomhammer, and the weapon of nearly every character on your list.
Let's not forget as well, that Warriors (the class, not the way you're using it as a basic descriptor) are magically empowered as well. Warriors in WoW have just as much magic running through them as any other class, it's simply manifested in strength and rage, rather than light, nature, the prime elements, death, or arcane energies.