I remember doing the same thing before. I found that sometimes you can get a bad batch of herl from time to time. Or rather there are better types of herl feathers that maybe come from different parts of the peacock.
I recently found some real long herl that is really tough to break, about 8 inches. This herl has not been cut and has the base of the feather still present. I might suggest trying some different herl brands and lengths since its pretty cheap. I have really tugged on this stuff of mine when trying to clean up an end and too lazy to snip it, and its tough, usually have to grab the scizo's.
I have never used the herl black ice before. Also if you loosen the tension as you wrap the herl to the point that it just slips through you fingers you will have less breaks. Good luck