The melds between MCH and BRD are a bit different to be honest. Bard gains a lot with skill speed(I never imagined I'd be saying this), while machinist doesn't benefit as much from it(ammo and proc chains rather negate it).

I'd never go with high skill speed on machinist. For bard though you should be looking at minimal ~600 skill speed.

For bard crit is still king due to the nature of our procs.