If this was original RD I'd recommend trying to get as little kills as possible since exp is wasted on all of Geoffrey's crew as they're all bad units with the exception of the main man Geoffrey himself. But now that they're not terrible this choice is harder. However consider that there's only 1 map where those guys will be forced to be used again in part 3, and now that every unit is pretty good, good units are not special. I think the "optimal" move is to sacrifice the entire team in 2-3 not because they're inferior characters, but because you can divert their resources to other units of a similar level, but you can't do that the other way around. But honestly, I think making the "optimal" move is probably more trouble than it's worth, and you just shouldn't fuss the details, kill what you feel you need to and don't be stressed about leaving stragglers. The gains from making the "optimal" move are probably inferior to the effort and stress in bothering to complete the map in that way.