Cutting the choice down to 6 possibilities:
- Core Race Tauren Druid
- Highmountain Tauren Druid
- Core Race Tauren Monk
- Highmountain Tauren Monk
- Core race Tauren Death Knight
- Belf/Nelf Demon hunter (speed twink)
Which narrows the discussion down to being mostly about class choice, since the different types of tauren function in pretty much the same way.
Some factors to consider
The most important part of herb/ore farming are the fundamental 3 steps that get repeated when farming:
- Move to a node
- Harvest the node
- Prepare to move to the next node (mount up)
Any farming advantages are usually connected to these 3 points. The core differences between the classes quickly comes down to how much time each class saves by cutting corners on the points they're good at.
- While the Death Knight's mounted speed bonus is stated as 20%, that doesn't mean they move 20% faster between each node. Move Speed bonuses are calculated additively, and not multiplicatively, and there's many sources that simply don't stack. Factoring in some likely elements (Maxed flying skill, The guild perk "Mount Up" and Pathfinder Achievement speed bonuses ), a small bit of testing revealed that the on the same account, a DK is actually a maximum of 10% faster between each node on the ground, and surprisingly only 2.3% faster when flying! Of course the testing was not perfect as it was done quickly using a script instead of actual testing (/run print(GetUnitSpeed("player") / 7 * 100);), but nontheless points to how DKs aren't actually wildly much faster than the competition between each node.
- Mounts have a 1.5 second cast time. For either Druid or Monk to be worth it over a DK, the 1.5 seconds saved from not needing to cast a mount needs to be greater than the difference in time between each node saved by the DK mounted speed aura.
- Monks using Zen Flight reportedly only have a move speed bonus of 100% in flighted areas. That's less than a third of what a mounted flying speed bonus normally is (assuming the skill is maxed out). Considering that both druids and monks can pick herbs while mounted, and the only benefit to a monk would be mining without dismounting. While this is nice for being lazy, it also means that monks will spend more than twice the time between each node compared to other classes, if using the Zen Flight method (which is really the only seeming benefit to monks). Mining nodes would need to be extremely close to each other for monks to be worth it in this case, but even then druid don't lose much time from remounting since it's instant for them. Monks are currently thus just plain worse than druid and are thus removed from consideration, since you would never pick a monk over a druid for this.
- A Feral specced druid moves nearly as fast as a DK on the ground, due to their passive Feline Swiftness which increased move speed by 15%, for a total of 235% movement speed in travel form (vs DK 240% mounted) while affected by the pathfinder achievement bonus mounted speed. But unlike DK, the bonus movement speed does not seem affect flighted speed.
- The guild perk Mount Up did however increase the speed of druid flight form, giving druids a flight speed of 420%, where DKs have 430%, which is not a big difference, all thing considered.
- I must admit I got no idea how fast a demon hunter can move, but I am going to assume it's not 330% faster than normal, even when stacking a ton of items and effects. So while they DHs may be better than the other classes at non-flying harvesting, they are probably safe to assume not the best general harvesters, as is the point of all this. DHs are thus removed from consideration.
This cuts it down to 3 possibilities
- Core Race Tauren Druid
- Highmountain Tauren Druid
- Core race Tauren Death Knight
Which seems to mainly come down to which is best between Death Knights and druids. The benefits of each class that I know about are as following:
Death Knight: Moves 2-2.3% faster between nodes than feral druids do (Constant) - Waterwalking, cannot be slowed below 70% (Situational)
Druid: No time spent on the preparation step (0 seconds to mount) (Constant) - instant mount type switching, water breathing, stealth, passive move speed bonus in non-mount areas, slow fall possibility (Flap). (Situational)