IANAB either, but pack survival could have a role in gene transmission, it would just be more indirect. Suppose pack A is full of extreme non-depressives and B is depressive. Highlander style, only one male in A will survive while B can maintain a back-up stock in case accident befalls the alpha.

That said I don't see why the gene expression couldn't be:

if (alpha) { act like alpha } else { act depressed }

individually beneficial and pack beneficial simultaneously.