I haven't found anything that manually mines as fast as an Ars Magica ranged AOE Dig spell, cast at mid-level augmentation (half moon). This level mines a 5x5 area, and you can spam it as fast as your mouse finger can twitch. Mana cost and overload is a small consideration, but didn't prove a significant hindrance so far.
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Edit:
It's possible some of the Blood Magic tools are faster, but they use up life essence. AM2 mana regenerates automatically, and if you learn the mana regeneration talents, it's fast enough that you only need potions for AM2 boss fights.
You apparently haven't seen what can be done with an advanced Blood Magic spell then. It dwarfs the bound pick axe. Also LP regenerate automatically with the right setup as well =)