I've never participated in ToO, are there 200 damage points like there are in the crucible? If that's the case then Ice Breaker's impact is so high that it would still do enough critical damage to overcome the damage resistance. I can't remember the numbers but I think it's around 420, so again, if that's the case, that's enough damage to one shot kill two guardians. And since I don't have any numbers in front of me this is all estimation, but the damage resistance of a 310+ from a (let us assume) 280 using ice breaker definitely would have to be over 50%, which at 50% would make critical damage for an ice breaker still more than 200 points, still one shot killing anyone in crucible (without overshields of any kind). So, light levels DO make a difference with standard weapons (primaries) but the damage from snipers is supposed to be stupid high because who in any relatable space scenario would survive a headshot from a sniper rifle?