Sorry if I've missed this:

The Strength in Numbers card allows you to activate two 'groups' whose development card cost doesn't exceed 12.

Is 'Group' a keyword only for multi-figure deployment cards? So officers, probe droids, unique figs do NOT apply?

Also- really pedantic... when two Stormtroopers are killed, it's still a 'group' since it started with three, right?

A

Check the section for Group in the RRG.

Group applies to all deployment cards regardless of number of figures.

E.g. Luke Skywalker is a group of one guy.