So are we basing our mourning off of exhibited talent? Should we then mourn the likes of Gadhafi, Bin Laden, Hitler, Stalin, etc because of their talent to control people? After all, it's a well-exhibited talent. Or is that not a talent worth mourning?
There are talents and talents, and talents for evil don't qualify.
On the other hand, does one actually mourn a person because of his talent or because of the person itself? This is very badly worded, but nevertheless puts an interesting question.
I can tell you I'm not mourning Brubeck or Murdoch's mum, and I can say that I mourn Niemeyer, but do I actually mourn him? Certainly as TK said, he cannot divorce the talent from the person. It is true, the talent is part of the person as the person influences the way in which his talent is expressed.
This brings me to a personal conclusion: there are two reasons to mourn somebody: because you appreciate his talent, and because you appreciate his person, his way of being. We could add "because you know him and love him", but that would be included under appreciation of the person.
In any way, you are mourning his loss as both a person and as a talent, because they are both indissociable from each other, but for one of the two reasons. One cannot mourn a "statistic" because one cannot reduce the magnitude, the scale of it to the sum of the individuals, and cannot identify himself with it, whereas the death of a person of proved talent and/or great personal value allows for the person to identify the loss, because without said identification, mourning is not truly possible.