My Rogue is a Engineer/Miner who had to recently spend some special time leveling up her mining level so that when she steps into Outland she can start to mine right away.
My Favorite Place To Level Through The Thorium Grind
My favorite place to mine for Thorium is just inside the Blasted Lands zone from the Swamp of Sorrows side where, to the left of the main road that leads you towards the Dark Portal into the Outland, there's a Nethergarde mine.
The mine itself was somewhat eerie for me to wander into the first time when I was getting my BS/Miner Warrior through the Thorium Levels - by that time I had already obtained the Netherdrake on my 70 Hunter and spent a lot of time in the Netherwing Mine on Netherwing Ledge, and the maps of these two mines are identical! Sure made it easier to make my standard loop through in an efficient way, like when I was scouting for Netherwing Eggs!
With my low-50s Rogue, I had to sap the guys next to the mining nodes, but with my Warrior being a few levels higher, I just stood there beside most of them and mined their ore away from them.
I had to kill a few here and there, but for the most part the mobs are spaced out well enough that there was no problem taking out the one or even two who had aggro'd me. Most of the mobs are mining with their backs to the wide tunnels, too, making it even easier to run past the majority of the mobs in my quest for ore.
Saving Travel Time While Leveling Mining
When I'm leveling mining, I tend to find that it's more economical for me to "park" that mining toon for a week or so - keeping it close to where it can hit the mining nodes. Then, I log in periodically and take my toon through a "round" of wherever it's mining and when I reach my starting point (takes less than 15 min in most cases), I log back out and come back later. This way I'm not wasting time flying to and from these far off "sweet spots" that I've found in the game for levelling up my mining with limited competition.
I'm not sure that area would be terribly great for actually farming stacks and stacks of Thorium - there are probably better areas for that, but this is a great one to make the rounds of and level up to 300 without it being too painful.
Where's your Thorium Sweet Spot? :)