People are bad at this game

[JonBigwood]

The restriction is the minimal gear to pass the dungeon. If you need to overgear the game to complete it, you are terrible.

I think the restriction means you cannot enter below that level because most probably you would make the group wipe (that is, just one player under that ilevel would probably make the fight too difficult to win reasonably.) This does not mean that a group composed with everybody at the minimum ilevel would be expected to win, but rather than a group with only one player at the minimum ilevel, if the rest are not, can be expected to win if played reasonably well enough.