Christian Slater is the best actor of his generation. There, I said it.
No, you are correct on this. No spell that causes a global cooldown can be combined in such a way, the only way to do that is to either use a conditon like [stealth] before it, or a castsequence. And there's no condition like [behind] or [infront].
If you're really set on not changing your buttons around for different situations, Daisuke, just make an alt/shift/etc modifier macro for mangle and shred like the ravage and rake macro. It won't let you autopilot but it's not that bad to hold a modifier down when you see something turn and start beating on *you* for a couple seconds.
With the increase on mangle duration and the high chance you will have a bear/arms in your raid to debuff for you, "stacking" mangle and shred clears up space.
#showtooltip
/cast [mod:shift] Mangle; Shred
Change shift with a different modifier if it feels more natural to hit, of course
Daizuke,
The reason there are no positional conditions for macros is so rotations can't be reduced to an automated script (botting is bad enough as it is, imagine if they carried the same functionality as a real player). You will not be able to create a macro to switch between moves based on relative position to the target. The best you can do is use modifiers, as many people have already suggested. If your problem is moving buttons around, you should technically be using both Claw (or Mangle at higher levels for feral) and Shred, so there should be no need to move your buttons around.
“Society is endangered not by the great profligacy of a few, but by the laxity of morals amongst all.”
“It's not an endlessly expanding list of rights — the 'right' to education, the 'right' to health care, the 'right' to food and housing. That's not freedom, that's dependency. Those aren't rights, those are the rations of slavery — hay and a barn for human cattle.”
― Alexis de Tocqueville