You are correct. The vocative is the same as the nominative in all declensions with two exceptions. In the second declension the vocative masculine has a different form in the singular (but in the plural it is the same as the nominative plural). Second declension nouns that end in -us have the vocative in -e, second declension nouns that end in -ius have the vocative in -i.
flebile nescio quid queritur lyra, flebile lingua murmurat exanimis, respondent flebile ripae