I noticed this very interesting phenomenon that happens when u party. I will give an example. During a fight u are attacking the monster and getting skillpoints for it. At the end of the fight, you only earned physical experience points. The other team mates got around 100-300 skillpoints. The next fight, it changes, now you got the 100-300 and someone else got zero skillpoints. On another fight, everyone in your group got some skillpoints but one person gets more than the others ie 90,130,200.
My party mate thought it was a "healing bug that steals party exp" while I think its part of SE's design to distribute skillpoint gain so there is no unfairness.