Spinal Cleave issue

Has something changed with the Qutrubs in Arrapago Reef? I'm trying to get Spinal Cleave, but I can't get them to drop their weapons for the life of me. I've tried standing on their right (weapon) side and in front of them while using crit and multi-hit BLU spells and WSs. I've also tried standing between the right side and the front. Despite all of this, I've killed dozens and never once seen the weapon drop and therefore the desired BLU spell.

If it matters, I'm currently level 65, though I started farming them at level 63. They're still IT+ or IT++, but I can still hit them. Also, at the start of the fight, some qutrubs have smooth, curved blades, and others have notched blades that look more like hunting knives than swords. Does this matter?


Update: After more work, I've managed to know his 1st weapon out of his hand twice, both times (I think) with Jet Stream. I also think both times were against qutrubs with the curved blade. I don't know if that matters. Success rate at knocking the weapon out is still very, very low ... maybe 1 in 20 qutrabs. (I've seen Spinal Cleave both times, but failed to learn it.)

Alright... so I finally got Spinal Cleave tonight. :-) It seems that critical hits have a better chance of breaking a weapon when the mobs are DC or easier. Also, I never managed to break the weapons when the "sword" looked more like a hunting dagger. I could only break the scimitars. But that's just my experience.