I know the story.
And frankly none of it makes sense. Not even “it’s just fantasy magic” sense, either; it’s just plain nonsensical in its concept, portrayal and explanation.
An orc attacking Sargeras is like saying an orc attacked Azeroth. A planet. Starting from a distance at which he could see that planet as a planet. Which means basically in orbit above that planet. So he was in orbit above a planet-sized titan, then ran on foot toward that titan - hundreds of miles - all the while fighting hordes of demons to then smack said planet-sized titan in the leg.
The extraordinary feat wouldn’t even be wounding him; it’s that somehow Broxigar could apparently run hundreds of miles in the span of a few seconds.
Never mind that for the actual Sargeras to have entered that portal, the portal would have had to be physically as large as Azeroth. Despite it being contained in the Well of Eternity. Which is itself significantly smaller than ancient Kalimdor, let alone all of Azeroth.