My LDoA title character, Alexia Wonderland, is at level 19.

I have 8500 XP to go, and I’ve found a run that will get me there tonight.

Do the Farmer Hamnet Vanguard quest.

Start at Foibles.
Turn left toward the Stone Elementals.
Kill the LVL15 enemies here
Head toward the river
Follow the river.
Don’t go into the town, though you may find a few Bandits at the intersection
Keep going until you hit the end of the river.

Map travel back to Foibles..

~500XP per run (Level 19) in 9 minutes.

Here’s the map:

Farmer Hamnet run to get Guild Wars Level 20