I've always thought a maximum EXP per day would be a better idea to manage that sort of thing. allowing that player to still boss/play
The only problem with that is to balance it right for the higher levels the exp per day allowance would be so big that 80% of the players wouldn't ever hit it daily anyway. so then as a team you ask yourself is it worth peeing off 20% of the server population because they enjoy playing your game for hours upon hours?
and the answer is no.Its really not worth it.
I find it frustrating, just like you that we can spend all of our available time leveling but will never be as high a level as these people that can play longer or do share accounts.
I have just come to terms with the fact that I'm doing as well as I can possible do with the hours I have to play.
Sharing that time between leveling, guild bossing or solo sub'n for cash you will never be the top of any of those games.
I'm mostly content (occasional rage) at being mid to high in all of those areas.