Depends on the group, my locks I waited a few levels after 60. the shams I did it at 59 no problem. The last boss you can forget until like 65. You can't kill the dragon first anyomore. Its funny I can down bosses in Mana tombs, and other instances that are harder just fine, pre Rock elemental tanks to help out is a reaaaaalllllllllllllllll bitch even with a tank on that dragon.