Btw, if WoW was designed to not be "silly" why have the items in the game in the first place o.o?
World of Warcraft has a design aesthetic that limits silliness, not omits it utterly. We all like a laugh now and then. That's why we have so many fun novelty items, easter eggs and humorous quests. Still, with a handful of exceptions, there's been a pretty firm line drawn between what amounts to a novelty item (which we anticipate players showing off occasionally for a laugh, or to enjoy on a temporary basis), and items that we intend players to use in their day to day activities.
It's that handful of exceptions that are the sticking point. It's the items like frying pans, cleavers and rolling pins that we're not sure we want players running around with on a constant basis. The jury is still out on that.
So what's preventing players, in their day to day activities, from using:
Or is chucking a tree as a Pygmy Gnome while your resident Ogre Hunter fires critters from his weapon not crossing that seemingly arbitrary line of silly?
I'm sure that there will be those that still find ways to make the most ridiculous outfits possible despite any precautions we take. We can't possibly anticipate every permutation of gear combinations that people will come up with, but we can strive to design the system so that there are fewer completely ridiculous looking characters running around. Yes, that's partially subjective. Yes, we also have a design aesthetic that, even with the introduction of the Transmogrifier, we still want to adhere to. No, I don't care if you personally think that any given tier set looks "silly"; that's not what's at issue.
There's a certain precedent that Blizzard has established in their game. A precedent which includes fun, if silly, moments like a Dwarf punching Deathwing in the face, or a certain recurring character who insists on jumping off of boats or pretending to be a Man-o-taur while surviving. If what you're going for is a silly threshold for the sake of preserving immersion, I assure you, you've crossed that threshold the moment you folks scripted Mandokir and Jin'do's dialogue.
There are also NPCs who fight with whatever they have, like Farmer Solliden, who sports a pitchfork. And our heroes are supposed to take them, as well as others who fight with worse, seriously?
And that's not even addressing the companions one can drag around into pits of horrors and against unfathomably dangerous characters. A balloon? A child? A turkey who throws itself into campfires?
It's a little late to pretend there's any threshold to seriousness in the day to day rigors of WoW. The bottom line is, the people who want to look ridiculous will find a way to do so regardless, as you said. So why fight it? Or, perhaps, the better question, why fight it halfheartedly?
You guys seem to be so set on imposing arbitrary restrictions that contradict what's already available in game (What's this about Tanking in dresses or "cloth," Pally T10 would like a word with you) when you should be letting players use this the way they want to for the reasons they want to: To look how they want. I don't see why this is so terrible, particularly when you give them the means to override their appearance anyway.