With good DW Fury gear speccing into Arms will lower your dps at your progression.
Do WWS on a raid and see how much physical damage is done on the bosses, add 4% on that.
Now the hard part is to see if these 4% extra dmg is greater than the dps loss you would entail by speccing out of DW fury .
And remember these 4% will only be effictive on NON bleed immune bosses.
It's also a matter if your 2h gear is as good as your DW gear .