For my part, I'm using more Crit, because I'm playing both MCH AND BRD. I guess DH could be useful because it's more stable than Crit, and that sound better for Wildfire.
For SS, I will not go higher than 555-655, because the best GCD for the MCH is 2.47. Lower and you'll miss a GCD in your WF, higher and you will clip too much + too much Heat generated during a short timelapse.