You wanna exp buffer, which doing nothing but running behind you, the Party EXP arent made to make bufferleveling easier. Normaly you would party up with another dmg dealer or mage or w/e, so exping then would be way faster.
So you mean we should increase the level difference for getting regular XP in party. That would just make everyone powerlevel using a friend’s high level character, and the whole leveling aspect would become pointless. Our XP rate is higher than L2x (I have proof for that) so it should be fine. If you wanna help out a friend who just joined, make a low level char or de-level your char (de-leveling is extremely powerful as you keep the high level spells, lots of people used to do that in L2x when we were in leveling parties). If you are level 50 with level 74 spells, you are going to level amazingly fast.