Dual-wielding attack speed slower than intended

When using dual maces, with the same attack speed on both, skills which does not have an attack speed penalty while dual-wielding, such as sunder, is attacking slower than using a single mace, as shown in the video below. Dual-wielding is considerable slower.

https://youtu.be/0dspYzx6nlU

This happens with every single skill, only sunder is shown above to showcase the point. I noticed the same behavior on Rolling Slam and Boneshatter, where both does not have an attack speed penalty.


Also, skills which have a attack speed penalty, such as Volcanic Fissure, appears to be much slower than 30%, shown in the video below:

https://youtu.be/oo_BgKm7mTk


Based on what I know, dual-wielding does not have a attack speed penalty, so it appears to be a bug.

If I missed something, please let me know. Thanks!