I've seen alot of people recently AoE killing 2+ mobs during leves, I'm hoping they weren't using their GA.
The best way to get SP in Leves is with GA on and using your lowest damage atk that you can and survive. It ensures more hits which increases your chances of getting SP. Since SP is boosted with GA on... you don't get SP for AoE kills, at least in my experience.
Same goes for those grinding, if you're only grinding XP then AoE kills are the most efficient... but not if you're trying to grind SP. (Honestly grinding XP doesn't make sense to me as you'll get more XP than SP always and there's only one PL vs multiple Ranks of Classes).