• Experience gained, including all sources of Bonus Experience, is now averaged across all players in a party that are eligible to receive experience
The patch note is kind of phrased weird. If I were to interpret that literally, I would say that they are taking the exp received by each character and splitting it evenly among all characters. Or maybe that they are just splitting the bonus. Who knows. It's pretty clear it's a move to silence all the whiners about certain builds being unable to gimp themselves into an XP build and thus the builds that can disproportionately benefiting; so if their implementation is not "fair" I'm sure there will be more outrage on the forums.

That said, I have no idea how you would test this...