Mentoring sounds like a PLers delight. You become the level of the person you are mentoring. I don't know if that means you become the level of the highest member of the group or average or what. Your equipment and spells also downgrade to the appropriate level.
Basically, on the positive side, it will let you group with your buddy who's too low by current level limits. It will let you stick with your guild groups even if you are the highest person in the guild.
On the minus side, for those that have issues with PLing, it will make PLing easy. The way they described it, if you have that uber 50th level RAID drop sword, and you group up with a level 20, your sword will be the equivalent of an uber 20th level raid drop sword. So you will still have superior weapons and armor if the weapons and armor are superior at your normal level. Which means power gamers in power guilds will be able to PL themselves or their friends in some major ways.
I know the Paludal Cavern comment always comes up, but this frustrates me. Did it ever occur to anyone to say "hey Mr. Level 60 druid, would it be possible for me to join up with your level 15 twink, please?" I used to PL at the back wall of PC myself, with my level 55 druid, because I really liked PLing a char to 20 or so. It was fun for me. And if anyone had ever come along and asked to join, in a polite manner, I would have let them. I say if because it never once happened. I did have a few folks ask to share the area and as long as the request was polite, I would stop pulling about half the area, or more if they could handle it, and I would occasionally buff them and heal them up or even rescue them. That was rare.
Usually people would move in like I had no right to be there and try and take over, or try and train my lowbie. LOL. Like I couldn't handle their trains? Usually they got themselves killed, or screamed for help and I wouldn't help them. I realize that many feel I had no right to be there, but frankly, who the f are you to tell me I'm playing the game "wrong"? It was perfectly legit within the rules of the game, while not a socially accepted practice. I was there first, I was polite, and if you were polite in return, I was very helpful.
Yes I was using a semi-choice spot. I finally gave up because of all the idiots that felt they had the right of it, and I was a jerk just for being there, and moved to another spot in PC and got better xp. The bandit camps are nice but not worth the hassles.
90% of game problems would go away if people would simply be polite and communicate in a polite manner.