Some time ago I had an idea on the HZ mIRC, about this way of making xp, so no one could leech again : The xp gain is determined on (and you only get bonus for group, and basicly if you do these you get a larger % of the amount of xp the monster gives): the damage you do on monster (get a x % of the total monster xp given normally) + the amount of healing you do in that time + the pulling of a monster from a crowd succesfully (scout) + the damage received by monster (this meaning that if you're the only one attacked by the monster/s, then you should receive more xp than they receive , and this could be a bonus xp for getting attacked) ......
Also, if it would be a lag problem, then what if the client (each group member) receives the info on the damage taken , given by each player and healing done, the client is used in the eventuallity if there is a group, and each group member's computer calculates the xp gained, bonus and percentaje, and sends it to the servers, and then in order to make things safer and error free, the servers take all xp from each members calculation (member calculates each member in group xp) and compares them to other members results, and the most close to eachother are declared correct ....
more ideas are welcomed ....