- Even mid-level content should be challenging. Being able to bring along a LV 50 buddy will water down the challenge yet again (see guildleves). Counterargument: If you want challenge, you are free to enter those dungeons with other low level players. Don't force your challenges on others, though.
You should also add there are people who don't have jobs below 25-30 anymore. If they want that challenge then they are screwed. You should not be forced to level another character just to get what you want (the challenge not the gear) out of a dungeon.