By the "everyone needs" argument, that means you "need" body as well, because every character will take damage at some point, and then it becomes a slippery slope argument, because every attribute is "needed" within the scope of shadowrunning. However you're not going to have enough points to cover every contingency, and the game is designed around the conceit that you will have areas where you are deficient, but your teammates should be there to cover that weakness. Have a clear idea of what the character's role is, and focus your character creation resources on that role.
To me, getting the best bang for your buck requires more than just a karma evaluation, it has to take into consideration how you're going to play the character. If the character never has to roll a certain stat, devoting resources to that stat is a waste, even if that character has, mathmatically, more karma than a different distribution.
As for magical skills, yes the two main ones are spellcasting and summoning, but every mage should grab counterspelling and binding as well. Now take into account you need some skills at the basics of shadowrunning, because not having to default on running when you have to gfto or etiquette when you try not be noticed as out of place is important. Which means that if you're thinking of doing any sort of serious attempts at enchanting, you're going to quickly run out of skill points unless you went with skills at A. Which, speaking of, is the best thing you can do if you are primarily concerned about karma efficiency.
It's easy enough to plug in the karma numbers and see:
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Total Karma per Priority for Humans
Priority Metatype Attributes Magic Skills Resources
A 200 425 215 469 225
B 165 355 125 327 137.5
C 110 285 55 203 70
D 75 250 N/A 146 25
E 20 215 N/A 126 3
Assumptions: Extra special attribute points were spent to increase the magic attribute to 6 first, assuming the magic priority is the lowest possible. Attributes and skills have placed all points in maximizing karma return per point (spending all points to the highest value in a stat before moving to a new stat). Resources are measured in 2k per karma as in character creation, however I don't think that is an accurate exchange, but it's what we have.
Under a strict what gets the most karma at each step, while being a shaman, a DBCAE set up wins, with a result of a total karma of 957. There might be an alternate path to get more, but skills A is just a monster and since magic has to at least be a C to keep being a mage, I kinda doubt it. The fact you can pump your magic back up to 6 with the special attributes makes this array a keeper, despite it being desperately short on nuyen, spells and edge. You could drop attributes a priority or so to recover spells or edge at the cost of overall karma, but nuyen's kinda stuck.
Now if you want any other race, your options are going to be highly limited if you want to keep a magic rating of 6. Skills A just so completely dominates the karma equivalency that it eliminates Troll mages as a viable choice if karma efficiency is one of your main concerns. Similarly, because dwarves are better at being a mage than orks, and dwarves and orks have the same priority costs, orks are out of the running as well, under this metric. If you go Elf or Dwarf, you have to raise race to keep a magic of 6, which would force attributes down to D. Without going thoroughly going through the options, I think elves and dwarves would come close and have some unique advantages (most notabily more drain dice and natural vision mods), but humans would both have more attributes overall (and thus more karma equivalency), and would be able to place those extra attributes wherever, giving them a flexibility elves and dwarves would lack.
EDIT: Math is hard before coffee.