i think abilities cant backstab, i only ever backstabbed in 2.0 with my normal attacks.
But its better to not use it anyways and better get consistently useful talents.
i havent seen it working with the double hit passive at all, can you make a screen or video?
And swift aim is very good with bows and stacking attack speed, just need to get a lot of it. 20% swift aim, certain items and other spoiler stuff, attack speed gets better the more you have of it.
I cant use my frenzy, meaning ui can issue the command, but it will clear the first millisecond in combat,
I CAN use it after i hit an enemy.
I have also seen my barbarian hit herself when i spam the frenzy hotkey, no idea what that was about.