jep, ase you assumed correctly, that used to be tied to crit. (pet crits) and you had the talent Cobra Strikes which was tied to Arcane crits.
so it was: Arcane crit => buff which makes pet crits => you gain focus (or something like that).
anyway, it was all too much dependant on crit (overvalueing crit), so they changed a lot to be some % chance on hit, only Go to the Throat is still dependant on crits