The crucible overhaul from last major patch isn't consistently applying the 15% damage buff that powered melee attacks were getting to compensate for increased player health. Due to this, weighted throwing knives no longer one-shot players every time you head shot them. Sometimes 212 damage is the highest it goes.
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The only time I've seen it not OHK to the head was if I died while it was in mid flight. Otherwise, I always see it do like 240 something to the head.