My mag and stamblade both use it. I don't think it's glitches, but it's one of their hardest abilities to use well and it takes time to master.
For me, they key is using it for the buff, then sometimes getting the bow hit as a bonus. It lasts for a long time, so I activate it then fight as per usual. The light-heavy hits don't have to be in a row...you have a full 20 seconds to get four in. When you do the icon flips and you get the free hit. Then activate it again and repeat. Mine procs all the time because I learned to thread with it. I also put it on a button I won't accidentally mash often. I like stacking it with siphoning attacks for some great regen and Dps. If I need to recover resources, I like the 30k kit at the end.
But honestly...it's a bit hard to use. I actually had to go kill a whole gaggle of unfortunate mammoths to practice the timing. Gaggle? Do mammoths gather in a gaggle? Whether or not they do, we are a lot of spectral,bow mammoth steak that night. Mm...Bowie.