FAIR WARNING: I am not at my computer, and am reconstructing all of this from memory, so not all of this may work as advertised, but I'm highly confident that I am remembering all this correctly.


The rebuke behavior you want is this:

#showtooltip
/use [@focus,harm,nodead][]Rebuke

This rebukes your opponent if you have a living,hostile focus, else rebukes whatever you have targeted.

For the focus behavior, I really don't know what you mean. You say you want a macro that "Set focus on my target" and then you say "if focus does not exists and I use rebuke on the target, this can't add this target to focus", which seems to be two exactly opposite statements. Either you want the macro to automatically add your first target as the focus or you don't. I'm thinking you really mean the latter, but I'll answer both because I'm bored.

Anyway, if you want the macro to set your Rebuke target as the focus, and remember it for the rest of the fight without ever setting another target as a focus, use:

/focus [noexists]

otherwise you may want to use a modifier key, like so:

/focus [mod:ctrl]

...which will set whoever you're rebuking as your focus whenever you hold down ctrl, but leave your old focus (including no focus) when you don't hold ctrl. The downside to this is that it can't be used if you have a keybind for ctrl+(key).

More likely, you just want a separate keybind for setting and clearing a focus, so you can focus whoever you want whenever you want. I'd probably use this:

/clearfocus[noexists][dead][mod:alt]
/focus[@mouseover,nomod:alt][nomod:alt]

This should clear your focus if he is dead or no longer exists, or if you hold alt, and focus your mouseover if you have one or your target if you have no mouseover--unless you're holding alt, in which case it clears your focus regardless. Remove the [@mouseover,nomod:alt] term if you don't want to use mouseovers, but you really should try it this way since this is super useful, letting you swap focus without targeting anything. You can use mouseover over the character himself, or his nameplate.

One quick disclaimer: I pretty much just PvE, and I'm not sure how this stuff works with an arena opponent that isn't visible to your client. If the focus macro clears your focus incorrectly when you hit the focus macro while your opponent is stealth/shadowmeld/invisible, you may want to remove [noexists] leaving just [dead]. Though I can't imagine why you'd be hitting your focus macro when you don't want to clear your focus or set a new one in the first place, so you probably want to leave [noexists].