If corpses are a lag causer, then why not move the corpses to the new graveyard zone as soon as the rez timer expires?
And, just to keep the players informed on what is going on with their coprses,
"The Grave Master tells you, 'Your essence can no longer return to your body in [insert zone here], Zorash. I have had your body brought to me in the Graveyard. Feel free to come and pay your respects to it and me.'"
It would definately unclutter the areas around LDON entrances this way at any rate.