Was looking for some macros, to do actions based on the number of combo points on the target.
Found a few, which was nice.

Unfortunately, CastSpellByName is a protected function now.
So cannot run:
/run C=CastSpellByName;if (GetComboPoints()>=5) then C("Eviscerate") else C("Sinister Strike");end

It would have been nice to Ferocious Bite at 5 combo points, but otherwise Mangle.

It seems the best will be either two buttons; a combo builder and a combo use button. Or to approximate how many combo points the target has, via a castsequence.