Gnomeregan is for either side and I think horde has at least 1 quest for it(as opposed to the 6 alliance get; Horde get a quest specifically -to- Teleport directly INTO gnomeregan from BB so yeah lol); pre-2.3, it was 30-34, 34 if you wanted to beat it, 28 was the accepted minimum; now with 2.3, it's down to 30ish at top end, small pulls until the end 4-Dwarf packs

If you plan on doing the final boss take a real player along or learn to multitask like a madman, as if someone isn't running around pressing the buttons to close the Bomb DIspensers, the bombs wil decimate you quickly