Let me hit it in the face: it should not be minmaxed to the highest dpser, it could equally go to a tank. Because this is a legendary, it takes a guild effort and guild decision to grant it to someone, and that investment must be done wisely.
People can leave
There are many stories of this and previous legendaries going to players who then quit the game or leave the guild. This happens a lot.
If that person was a dpser, then you just lost all their extra dps power when they walked out the door.
If you had a tank, who wanted it, and is still in the guild after the deeps has left, then you’ve just wasted all that effort and put a really bad taste in everyone’s mouth.
Therefore, do not make it a decision solely based on dps when there might be a better candidate who is a tank.
It is a recognition
The gift of Shadowmourne is also a personal responsibility, as most people also need to earn the saronite bars by themselves. That is a serious effort and cost. If the guild decides to cover some of that cost, then the gift is even greater; this should only be done where there is a great commitment from the player to the guild.
Eventually, the weapon will be replaced in Cataclysm, but it will not be vendored. The pride of having carried this weapon will remain.
We’ve been discussing whether you should gear differently around Shadowmourne because it has no expertise.
I wrote a ranked listing of the weapons you can get for DK tanks.