Lorewise, we exist.
I know our actions are often rationalized as "Lore character was defeated/assisted by a group of heroes" or champions or whatever, but the fact is... we exist. And we have had genuine lore-effecting effects on the world, with actual consequences.
But I'm not talking about "We slayed this dragon, saving the zone" or "we slayed this mechagnome, saving all life on Azeroth". I'm talking about the negative effects. I'm talking about the screw-ups, minor and monumental. What are some of the worst mistaked made by the Horde/Alliance "champion"?
The biggest/most obvious one I can think of was the freeing of Gul'dan & Cho'Gall at the AU Dark Portal. There were so many ways to repell the incoming Iron Horde invasion, but we made a split-second decision to precision strike the two batteries keeping the Red Dark Portal open: the imprisoned Gul'Dan & Cho'Gall. For all their power, both had been successfully taken down and placed into submission by Grom Hellscream and we let them loose, sparking a chain of events that would lead to The Broken Shore and the 4th war.
One could argue that "everything turned out for the best", but we still saw a decrepit old orc and a two-headed ogre writhing in bondage, and we let them loose and cheerily waved them goodbye as they fled into portals. But hey, we closed the dark portal and stopped some iron-clad orcs from spilling into The Blasted Lands. That's the important thing! What's the worst that can happen?
Even small ones are fine, like killing Oregorger in Blackrock Foundry. He seemed to be performing a community service, and killing him and his brood seemed to serve no purpose, and in fact actively distracted us from why we were in the foundry in the first place, giving our actual target ample time to rally defensive forces and endanger our entire mission in that place. We took a wrong turn in Blackrock Foundry, and instead of coming to a dead end and turning back around, our faction's "General" (our rank at the time) decided to moronically endanger everyone's lives by eliminating something sabotaging our enemy.
Any other "brilliant" decisions on the part of Azeroth's "champion"?