Meh, the 40% loss is önly that "small" due to their attacks missing. Their optimum drops from a potential 120 wounds to a mere 58 (29 bites, 29 celestial weapon). Which is roughly a 50% loss. And frankly even a 40% loss is kind of unacceptable. To be honest, a bigger issue than just getting them in range is to get them to survive for long enough to actually be worth it. Getting multiple rounds of combat with 30+ models, even if only 20 or so are in range will rapidly overtake the effect of 1 round with 40 only for them to be decimated afterwards.