[1.1] titan's Breath spell

Noticed this in all 1.1 games I've played - the spell Titan's Breath, from the air book, which is supposed to move the target to a random square on the tactical map? It doesn't appear to do anything! This bit me on the arse when some overzealous dungeon exploring lead to me facing a 119hp, 38 hit hoare spider who went through my padded armour and boar-spear wielding sovereign and army in fairly short order. Titan's breath utterly failed to move it, so I never got the chance to exercise the Monty Python school of combat with "run away, run away!!!"........

Am I missing something? Is it linked to intelligence (18) and size / hit points of monsters targetted? only I tried it with a swarm spider and a darkling as well, same result.