I agree that there should be a minimum ilevel requirement for dungeons. There should also be a minimum ilevel requirement on each individual piece, so that one would not be able to use a low ilevel weapon - which has the most impact on damage - with high ilevel accessories. They could make the ilevel requirement for accessories lower than the ilevel requirement for armour and weapon, since people might not want to upgrade their accessories as often as their armour/weapons.

Other suggestions which people have made in this thread:
- Minimum main stat requirement, so that one cannot use DoH/DoL equipment.
- Job crystal requirement when at or above level 30 - perhaps enforce the requirement when they are level 35 to give them a little freedom in when they choose to complete their job quests.
- Putting people in a leveling dungeon appropriate to their ilevel - there is the potential problem of people avoiding certain dungeons by equipping lower ilevel gear, but since this would only apply to leveling dungeons, there isn't much benefit to be had most of the time, since they'd just be getting less Exp.