Now on topic, I want to say that I agree with adding a min. ilevel for the various dungeons in HW. Force people to actively invest in their gear and make them realize that they actually need to gear up, it's a good thing to know once you reach level 60 that you'll need to gear up at some point if you want to keep going. Now, with that being said, I don't think that the ilevel is generally a problem until you reach two specific points in the dungeon content.

The first point is when you reach Nidhogg, when one dps that is geared gets hit by Sable Price, the undergeared dps is almost never able to actually break them out of it and as a result they die and makes the rest of the fight that much harder, not only that, but it can also make you struggle on the add phase, and with burning him down after he does Massacre and starts to spam his aoe damage attacks at you.

The second point where it really becomes a problem is during the Vault when you reach the second boss and third boss, both of whom can potentially overwhelm a healer if they aren't killed quickly enough by the party as they can be very taxing on your mp with just how much damage they can do. There have been times where due to those bad dps I have been legitimately unable to clear those dungeons even when I would go Cleric as a healer or try to DPS stance as a tank. When you reach those two points it really starts to show. Vigil and Sohm Al on the other hand? Having low dps won't necessarily mean your group will lose, it just means those dungeons will drag on which, while boring, are still able to be beaten.