BLU can stomp level 70 dungeons into the dust with Basic Instinct. The only one that offers any real resistance is The Ghimlyt Dark, and it is only due to the first boss having an exceeding strong tank buster, which may kill you if you get overzealous with DPSing. If you really know what you're doing and don't die, you can clear most of them in 17 minutes or less.

Every tank at 80 can solo every level 70 dungeon in roughly 30 minutes all the way back to the first tier of level 80 gear.

DPS at 80 with access to self healing can solo up to about The Burn, depending on the job, and depending on your gear. In i500+ gear, stuff like RDM shouldn't have any problem soloing the level 70 dungeons.