I don't have a need for Misguided Rocket Battery since I already have the 3-6 incarnation of it -- Overcharged Rocket Battery.
As for why I fooded the Hollow, I have 2 Rusties, 1 Fractured, and one Hollow (all maxed), so a second Hollow won't benefit me since Hollow only helps in really specific situations where my stats are unstable when Rusty or Fractured is used.. But that occurs rarely.
And for Sparked Runners, I already have a mythical pair.