Is Slam/Imp Slam really so terrible as 2h Fury? Sure it resets your swing timer, but we've got swing timer addons to time that correctly now. And its half the rage of Mortal Strike but still does similar damage. It is still weapon damage plus some static, where the only drawback is that the static damage is about half of MS. But its also half the rage.
Pretty sure Slam triggers Flurry if it crits but does it use up a charge? Flurry makes up for the DPS loss for the cast bar of Slam compared to using instants like MS/Bloodthirst, so it looks pretty good on napkin math. Like, if Arms is assumed to have the rage to MS on cooldown, then Fury could Slam after every auto-attack. If Slam does trigger Flurry, you would need a lot less crit to keep it active since you are nearly doubling your opportunities to get a crit.