Not to mention, if you(tank) have a much lower(probably 50+ lower, not exactly sure on when it starts to really have negative affects) ilvl than the rest of the party, you will have a harder time holding agro. If I'm ripping agro off a tank extremely easy, first thing I check is their gear. Having ilvl50 gear in a 50+ dungeon means the tank won't be holding agro for very long.