It's Wreaking Havoc in Wyveria.

I've counted up **all** of the average rewards (including carves, wound/part breaks) from running each quest 3 times as if they are all converted to armor spheres via smelting.

I've been getting very inconsistent results with Tongue-tied, so I've run it 10 times and kept the decimals, but even then it seems to be the worst one on the list.

It's important to note that Doshaguma pack's completion time varied for me greatly (from 5 minutes to 9 minutes) and I fought all 4 at the same time. I had way more hopes for this one, since it has a guranteed Heavy Armor Sphere reward, but it seems to be not worth it.

I had a lot of hopes for 9 star Seregios, but it seemingly drops Hard armor spheres in stacks of 1, which greatly reduces the overall points consistency.

While "smaller" Tempered 9 star monsters (Mizu, in this case) have the highest armor points per quest, Wreaking Havoc in Wyveria on average will be much better in terms of points per minute. Fighting Arkveld specifically could boost it a bit, since his parts worth more, but as you can see parts contribute a relatively small amount of points compared to just getting Armor spheres.

Decided not to test lower star investigations, since they don't drop a whole lot of armor spheres in the first place.

Overall, not very surprising that dedicated event quest for farming armor spheres is the best one for farming armor spheres. Still, high level investigations are a pretty good way to farm them, considering it also allows you to farm charms at the same time.

So if anyone wanted to know what's the most efficient way to farm armor spheres, here it is.