Actually they are close to 600 DPS, Don't forget to include boosts for tanks and healers from litany and disembowel is still significant for BRD/MCH. The dragon sight is just icing on said cake.
When you factor in raid buffs most melee will likely outdo the casters by a bit. Napkin math puts Nin around 4500 and drg closer to 4600. Monk only goes up 100 or so to 4335. Please Note, napkin estimates since real parsing will show more accurate numbers (aka lazy and not figuring out compounding effect, crit damage increase values (it's not a 200% damage increase from crit), etc).
All that said, can't wait to see numbers on an actual raid to see how all the buffs compound and how high each class really is. I wonder if MCH/BRD could be dropped entirely, if healers don't need the MP...