Originally Posted by
zylya
The thing about the axe not requiring you to kill Arthas is lore-based: you forge the axe as a counter to Frostmourne, it wouldn't make sense that you have to kill Arthas to forge an axe to help you kill Arthas.
As for the obtaining of it, the problem most people found is that because it was all quested, everything was guaranteed - other legendaries (Val'anyr aside) have all been about getting lucky, whereas Shadowmourne is the first one where YOU were in control of everything you did to get it - no countless runs of MC for the Eye/Bindings, no luck required on Illidan/KJ, it's all down to the effort you put in. If you think about Sulfuras, apart from the Eye itself, there is no difficulty if you're clearing MC each week. The Eye doesn't make it difficult though, it makes it RANDOM. To me, random is not legendary.
And in fact I'd say that Shadowmourne requires you to put the MOST effort in, since no other legendary had as many things to do as Shadowmourne. The only difference is that you didn't have to rely on luck to get it, unlike almost every other legendary.