I don't know, I was thinking of a situation where your TG are completely mobbed by inferior units. While D6 str 4 hits hitting your TG isn't ideal, only 1/4 of the hits against your TG will wound, averaging to 3.5/4 dead models per turn (less than 1). Assuming you use this properly, i.e., when you are pinned by swarms of weaker troops, I think it is a spell to cast early in the magic phase and tempt your opponent to dispel. No panic checks while engaged in combat, and I think TG are Immune to Psych with the Slann anyway, in case you find that there are a bunch of units within 12" shooting the TG unit. Every enemy unit within 12" starts to add up in terms of kills, especially if they are weaker troops. Also, since you are killing a few models off of each unit BEFORE the combat phase, if you reduce their ranks they won't count towards the next combat. Other lores have similar and better versions of this spell, but I'm just wondering since I'm working on a full review of the lores of magic (with respect to the Slann).