Leveling from 47 to 58 can be done very quickly by selecting specific dungeon in group finder, and queing for Blackrock Depths Detention Block. The idea is to complete the dungeon in about 2 minutes in order to get the dungeon completion experience reward. As soon as you enter the dungeon, use the mole machine to teleport to “just past the grim guzzler”. Aggroing the adds across the platform can speed up the run, as they will run around and often aggro the last boss, Fineous Darkvire.
These runs are a good time to elixir buff due to how much additional experience can be gained. Occasionally the adds from the ledge don’t aggro Darkvire. In these cases, the group will need to take a minute to clear to the top of the ramp. When queing Detention Block again, sometimes the join as party button on the group finder will be greyed out. Another member of the party will have to start the queue in these cases. A player can only be in 10 dungeon instances per hour. Doing Detention Block runs can reach this limit very quickly. If you hit this cap before getting to level 58, consider taking a break and continueing later. Also, when queing into a random group, it can be best to ask people if they want to speed run. not everyone knows how efficient this method is, and some groups may want to do the run more conventionally..
As found on Youtube