Blood Barbs & Rend

Ive been running a Blood mage witch primarily using the Wyvern form to deal out lightening and bleed and I noticed something odd. The crux of my build was focused around blood barbs and using empowered Rend and other wyvern attacks to scale bleed magnitude to absurd Heights.

The issue came when I noticed Rend was only triggering Herald of Blood when NOT empowered. Double checking the stats on rend it still shows that empowered rend has physical damage so it should be able to proc bleed. its strange because Oil barrage doesn't have this issue and procs bleed in both of its forms.

I will do further testing to try and figure out the issue but wanted to bring it up since it seems like some kind of weird interaction/oversight