I think Superheating is still the best way to train Magic when you're foccused, since you also get Smithing xp

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Alching at one spot is a total waste of time, since you can also alch while training other skills!
For example, I train fishing at barbarian village and I alch a gold necklace after every fish I catch.
I still get the same Fishing xp/h as without alching, but also 50K+ magic xp. So the Magic xp is sort of "bonus" xp.
It's also possible to alch while training melee (with a scimi), Mining, Woodcutting and so on

Good luck!