BTW, fear stacks very, very well. Sombre mentioned my dirty horror trick which will rout any SC not mindless or berserk, but you can achieve a similar effect on armies rather than SCs. Horrors don't work very well for this because they spread out, but there are a number of fear aura units - nightmares, demon knights, ghosts, banshees, etc. When they engage in melee while clumped together it's pretty sick the effect on the front line's moral, each block gets hit by multiple fear auras and the moral instantly drops into the negatives most of the time. If you spread them out right so that this affects a significant portion of the enemy forces you don't have to do much fighting.
Now what I'm curious about is how the moral checks are handled.
Do multiple fear aura's trigger multiple moral checks?
Does a 100 man squad make a moral check for everybody if just one unit is within a fear aura?
Do you make multiple fear checks if you have multiple triggers - ie hit by agony while inside a fear aura while taking melee damage.