I could have sworn the limit was level 52, at least that's how it was a few years ago.
Twinked 52 characters have been known to solo Vox and Naggy.
Also, unconfirmed reports have indicated that sometimes it is possible for a high level cleric (or say Pally or Shaman) to throw a Heal over Time on participants in the fight without getting "deported" from the zone.
I could see how this could be true since sometimes when a cleric throws a HoT on a tank in a regular fight and he doesn't get on a hate list.