Well, I dont have PL'd chars, and probably never will so i guess i dont fit in your concept. But, i find funny how people tends to care so much about how others define fun in a situation where there is no way they could affect your gameplay by any way. If we had PvP, it could be an issue, but even then it would be a minor one.
Cheating could be defined as "stealing" resources from the world (game/server) by bypassing game imposed limitations without work or risk.
PL surely doesnt fit on this because SOMEONE is doing the job that makes him worth to get that resource (xp/influence). Someone is out there working for 2 people, not just for himself to get the other one xp.
So if it is indeed a cheat, lets take grouping as an example. Two people fight less on a group than they would be soloing for that same content. Still, they earn more xp.. Hmm.. sounds like cheating to me eh? The work/xp on a group is lesser than soloing and still you dont consider it an exploit/cheat...
So, I cant really understand your point, sorry...
Regards