Venomous Axe on Bards?

[Legidias]

It should be noted that off hand procs half as much as main hand though.

What song are you playing? If its a song that targets something, it will end when that thing dies (or zones). Are you hitting any keys? Depending on how its bound, hitting a spell gem key will stop it (I will go ahead and plug that using keys is better than a stopsong macro).

Missed notes won't cause your song to stop. Once you're playing a song, you won't get missed notes (those are basically fizzles from other classes).