There is a tremendous amount of meme potential in 5vs5 because of several factors; diffused responsibility, decreased impact of individual spec balance and the fact that the 5vs5 bracket is a PuGfest with carries and trade-chat groups generally lowering the skill floor of this bracket compared to 2vs2 or 3vs3. This means that nearly anything can be effective up to around 1900 or so in 5vs5, AND the bracket awards about 25% more arena points than the other brackets. So 5vs5 is seen as, oddly, one of the most approachable brackets.
Weird things I’ve seen work in 5vs5? FIVE Shockadins. FIVE mages. 2xRogue/2xFeral/1xRdruid. Could you try to just delete some teams out of the gate by stacking a bunch of PoM-Pyro mages? Sure. The gimmick would work for a long time, too. You wouldn’t be winning against REAL comps with sweatlords at the keyboards but you could probably take wins off of most disorganized tradechat pugs.