The mentor penalty makes sense when there is a healthy low level population. It incentives players to join groups at their own level instead of levelling up by doing trivial content. Which means low level groups are more likely to invite other low level characters because high level characters are in high level groups. And everything is balanced and happy.Question I just thought about.. Why is there even a Mentor Penalty?. What problem does it server? Is it an artificial XP reduction that actually servers no purpose in game play?
But when the population balance shifts to high level characters and getting low level groups is hard, the mentor penalty is counter productive. When there are no other low level characters to invite to low level groups, you want high level characters to join and mentor so you can fill the group and do content and get rewards.
Other MMOs incentivize "mentoring" with bonus coins/tokens and unique appearance loot, because they want new characters to be able to do the content. So they find ways to make it rewarding for high level characters to group with them and do old content. The server will even form the groups for them. This is something SOE/DBG/Darkpaw has never been able to get right.