If you want to reach skill level 800 in mining really fast, this method is perfect for you. Getting from level 1 to 800 will probably take a few hours in total. To use this method you need to have the add on called Cross Realm Assist, and an active Massive Leystone World Quest active.
When you got this, go to the world quest location. Turn off auto loot, and mine one of the nodes for the quest. Now walk away without looting the item, and mine every single node you can find in the area. Don't loot any of them!
Once you have mined all the nodes, click on Quick Join button on the Cross Realm Assist add on to change realms, and now you can skill up using all the same nodes once again. Keep changing realms until you reach skill level 800!
The problem with this method is that remining the same nodes on the same server does not give skill up, so every once in a while you will be back at the same server you already mined. If this is the case, and you don't get a skill up from the first node, simply realm jump again for a new server.
Also note that once you leave the area, the ores from the World Quest will be mailed to your character, so you don't even loose out on the WQ loot for doing this method.