Yes, we’ve deployed hotfixes to address a lot of what was happening here.
The ranges are based on the level of the last boss in each dungeon. Now, all classic dungeons should allow a range of roughly 8 levels: from 3 levels below the level of the final boss to 5 levels above. Burning Crusade dungeons should now allow a range of 3 levels below the end boss to 3 or 4 levels above it, and Wrath dungeons allow a range that starts at 3 levels below the end boss.