I realize that, because we're still in the Beta stage, it's too soon to spend much time on recalculating the "Rules of Thumb"; still, I've been thinking about how the "Super ***" outsiders affect leveling.
We have the recommended maximum levels in this post, but they have been significantly affected by the "Super"s. With a Super Dora level of 4, for example, leveling Dora to 150 has raised her calculated effect to 12829.49% for me -- but her maximum effect is 9900%, so I've already wasted souls. I'm almost certainly wasting souls by leveling Kuma right now as well, as with Super Kuma at 4, I'm ascending whi