I thought i wasn't going to make it to lvl21 too before the new level cap comes, cause i used to level on regular maps. Then pandamoni showed me watchers tomb. It is insanely easy to level. Even with a bad group, it only takes about 10mins to run, and you get about 500-550 exp for the run (w/o exp elix). So it's only about ~32 runs to get the 16k needed from 20 to 21. Or if you can get exp pots, about ~20.