@traumabrew Shoulders pretty much always. Magistrikes only worth when you have constant cleave.
BD will help you get the CB's out faster, but if the lashers are dying before you can get a cast off I'm not sure what the problem is? Right now on live destro doesn't have amazing burst priority damage, if things die super fast you just don't have an opportunity to hit them and don't do much dmg to them. No ways around that.
If you aren't having a problem with those adds dying though, then I'm not sure what the issue is.