I just hit 80 with my tank warrior. I've read many places that say I should have 540 defense to start heroics/Naxx, but I'm only 470/26k hp. I used the WoW Armory to check for armor upgrades and where to get, but the mass majority of next upgrades for my items are in Naxx/Ulduar+ . I've got about 4 crafted epics, rest blues and 2 greens.

Am I misinterpreting something here? Good enough to start Heroic UK or Nexus?

I appreciate any answers I can get. Thanks in advance.