Shaman One-Shot Leveling/Gold Farming Technique (Patreon)

(Note: In Shadowlands all players can create Class Trial Shamans. Class trials have been suspended for the duration of the pre-patch.)

Enhancement Shaman have a level 38 ability called "crash lightning" which increases the next stormstrike by 5% per enemy attacked.

There is no upper limit to the damage bonus. By forming a group with a starter edition account character in timewalking phase it is possible to do the following:

1. Go to a zone you out-level.

2. Gather up  a large number of mobs and kill them with crash lightning.

3. Activate party sync.

4. Using the damage buff from crash lightning stormstrike mobs thereby gaining xp and level-appropriate loot.

It is worth mentioning that high-end loot has a much higher vendor price in timewalking mode, some weapons vendoring for over a hundred gold, so if you can work this effectively you can get decent raw gold per hour. 

This method can also be used to boost other characters. It can be used in dungeons but its execution requires some practice and skill since you have a very small window of opportunity.  

EDIT: partial nerf to 75% max damage on Stormstrike (thanks Mark, see comment below). Still somewhat useful as looms + buff should be enough to one-shot open world packs.