We will be soon be overhauling the benefits system to be formula based and actually give higher rewards than currently being given. I will detail the formulas here, and include a spreadsheet that shows the XP tables for both.
Party XP Formula:
If PC Level > CR of Killed NPC:
Formula for XP Reward = (CR * 6) - ( PC Level - CR ) * CR
Otherwise:
XP Reward = ( CR * 6 )
If a creature killed is 6 or more CR beneath your current level, you will receive no party XP bonus.
EX Mode Formula:
If PC Level > CR of Killed NPC: Formula for XP Reward = (CR * 12 ) - ( PC Level - CR ) * CR
Otherwise: XP Reward = ( CR * 12 )
If a creature killed is 12 or more CR beneath your current level, you will receive no EX XP bonus.
http://www.realmsoftrinity.com/Downloads/XPRewardCharts.xlsx