Looks like the dungeon level ranges have been fixed finally

[Zenetta-proudmoore (Zenetta)]

Yea it was hotfixed yesterday. There was a blue post about it in the bug report forum:

WOTLK classic dungeon finder - dungeons missing in level range

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.