I really would like an answer to this topic. Seeing as how it has some pretty serious ramifications on formations, this will greatly affect my deck build for the koteis and should be answered now rather than in the middle of kotei season.
formations and "opposing"
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from the Wayback Machine (its copy), so posts it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
I really would like an answer to this topic. Seeing as how it has some pretty serious ramifications on formations, this will greatly affect my deck build for the koteis and should be answered now rather than in the middle of kotei season.
Formations, including Rain of Death, will continue to work unchanged. Any rules change for formations will not occur until after summer.
To sum up, Formations give you relevance in their own right; references to "opposing" cards on formations need not be cards in the current battle, allowing effects to occur in battles other than the current one.
[Marty's Edit - Removed a reference to "Presence" herein. Formations aren't units, and thus don't fulfill Presence requirements.]