Added a sub-section explaining the usefulness of Vine to the existing section Building a well-balanced team.

Eidolons can supplement debuff deficiencies (to a point).
ATK down (-10%): Yatagarasu (9T), Jormugand (10T)
DEF down (-10%): Vine (SR, 8T)
Blind: Apocalypse (10T)
Affliction resistance down: Sphinx (9T)

The story SR eidolon Vine in particular is very important, as most teams otherwise lack the capability to exceed -40% DEF without specific rare SSR kamihime. Teams at the -40% DEF threshold can gain as much as 16% damage (-4% from low stats relative to event SSRs) by running Vine. Vine can be purchased in the event shop by players who’ve reached the Dark-element world in the story quests. Farming the necessary single copy takes only about 250AP once players have reached this chapter.

Note that relying on eidolons has a tradeoff: the summon ability typically won’t be available for 8-10 turns, and only one can be used per turn. This can be a significant drawback in brief encounters, such as Advent Ragnaroks, where the fight is usually decided before summon abilities are ready.