A marks/survival hunter's optimal shot rotation would be what the fancy-pants hunters call a 1:1.5 or basicaly a 2:3 rotation meaning that for every 2 auto shots, you're weaving in 3 specials (or 1.5 specials per 1 autoshot for people who like that ratio)....I think 2:3 is easier to understand because your shot rotation would go somethign like this..

[color=cyan:cf8d5b2a6c]auto fires[/color:cf8d5b2a6c], steady fires (while next auto is on cooldown), an arcane is squeezed in before your next auto,  [color=cyan:cf8d5b2a6c]auto goes off again[/color:cf8d5b2a6c],  steady, [color=cyan:cf8d5b2a6c]auto[/color:cf8d5b2a6c], steady, multi, [color=cyan:cf8d5b2a6c]auto[/color:cf8d5b2a6c], steady...and then it would loop back to start with [color=cyan:cf8d5b2a6c]auto[/color:cf8d5b2a6c] , steady, arcane again.

So it sounds like you've pretty much got it...every other steady should be able to fit in an arcane or multi at the end of your steady and before your auto without delaying your next autoshot which they refer to as clipping in those elitist jerk forums.

I don't know if that makes sense, but there's a graphic used in several of those forums to show when each shot is taking place.

Of course, your macro should have kill command in there as well so each time you crit your pet's damage is maximized too.  It sounds like you have the right macro that you slam repeatedly to get your steady/auto rotation...then you just weave in manually the arcane or multi on every other time around.

The macro is pretty easy to find in any of the forums, even the blizz ones.    I had to experiment till I found one that I liked.