Prison runs. Buy the xp anywhere elixir, buy the 75 plat shadow hunter elixir, and join First Class using a Rift portal. About 120-150k xp per hour depending on your luck and how good your team is.. Xp amounts vary. Make sure you boost luck as close to 100% as possible because boss drops up to 20k xp drops which are elite drops.

Find a team of higher level friends to carry you through the runs until you can equip higher level gear. We carried an archer from about level 56 to 80 in no time in my guild.

If you're not up for doing that, Mega Maze is probably still one of the next best alternatives with at least two people (one person on the inside and one outside).. But it doesn't compare at all to the massive xp you get from Prison.