In order to filter out the absolute nonsense let's restrict the discussion to alleged mass graves of that are documented in wiki ....
So, for example, the mass graves of NKVD victims are documented here ...
http://en.wikipedia.org/wiki/Vinnytsia_massacre
and the mass graves at Katyn are documented here....
http://en.wikipedia.org/wiki/Katyn_massacre
Note that the Katyn mass grave was discovered and excavated by the Nazis. The victims had been killed by the Soviet NKVD. This did not prevent the Soviets with charging the Nazis with the massacre at Nuremberg, and trials were held in the Soviet Union complete with confessions, convictions, etc.
A little googling reveals persons much more knowledgeable than myself have stated that there are no holohoax mass graves, and that the usual holohoax idiots, like Roberto Muelenkamp, Nick Terry, et. al., have responded to the issue on their blogs. So, the issue has been covered and is available to anyone who is interested ..... here is a representative example ....
http://rodohforum.yuku.com/reply/139663/t/Photos--mass-graves-containing-Jewish-women--children----er-.html
Note the Soviet cartoons of mass graves that the hoaxers try to pass off as legit, the total reliance on Soviet investigations in Eastern Europe, the lack of outside observers, and the lack of a written reports. Contrast this to the Nazi investigations that took place DURING THE WAR, and still managed to be transparent and well documented. To exclude this nonsense, let's restrict the discussion to wiki documented mass graves.
So, as the OP claims, there is not a single mass grave containing holohoax victims.