this is ridiculous. i encounter over and over arms warriors who avoid slam like it's the plague. many continue to believe it even reset your swing timer. the fact is, it is the bread and butter of arms dps and is simply replaced by abilities with slightly higher damage when rage permits it.
the most functional way to think of an arms warrior rotation is simply slam spam with every single slam being a variable. keeping that in mind:
sudden death>over power>mortal strike>slam is the priority in regards to damage, all the while keeping rend up.
a far as rage is concerned however, overpower>slam>sudden death>mortal strike
the problem is, warriors who prioritize mortal strike above slam with no consideration given to rage usage.
in low rage situation, you can even drop MS from your rotation if it means continuing slam every gcd. if MS would take you to an empty subsequent gcd, slam instead. that being said, in a raiding situation this is almost never the case, and MS is effectively a rage dump vs. slam.
the easiest way to think about it is with simply 2 gcds. you can mortal strike at nearly double the rage cost (considering slam's slight pushback of next auto) and not slam...or you could slam twice. where rage is a limiting factor, slam always pulls ahead.
what is complete garbage is when slam is cited as the rage dump, which is not at all true. using other abilities (minus overpower) in place of slam are the actual rage dumps. higher damage for significantly higher rage costs.
the easiest place to witness the efficiency of slam is at a dps dummy. self buffed, rage is often limiting. attempt a rotation with simply rend, slam spam, and overpower at procs. you will be able to use every gcd with dps just below where it would be with MS and execute. if your gear is good enough to substitute sudden death/MS for slams where appropriate, and still fill remaining GCD's with slam, this will net highest dps. but if you are replacing slam with sudden death/MS and left starved for filler slams, you will notice a decrease in dps.
point being: basic arms rotation consists of rend and slam. all abilities used are simply replacing a slam, and when not up, slam continues. if using an ability means locking out a subsequent slam, don't use the ability. (as stated earlier, this is hardly ever an issue in decent gear, raiding).