Learning Irish gives
a fheara ! "(you) men!". The Iorras Aithneach study gives
a fheara ! or
a fhearaibh ! for the same, but
a fhir chóir,
a fhir mhaith, etc., with an adjective.
gasúr is "child" in Connemara.
Learning Irish gives
A ghasúir bheaga ! "(you) little children !", but no example without an adjective.
The Iorras Aithneach study gives
a ghasúir,
a ghasúr as the vocative singular, and contrasts it with
Gaeilge Chois Fhairrge: an deilbhíocht, de Bhaldraithe (1953) § 40 but I don't have the latter or know what that means.

An Lon Dubh wrote:
However I can't think of a situation where you would really say this ("Two dogs!" rather then "Dogs!") and even addressing animals is rare.
(Even Old Irish did not have a vocative dual).
A dual vocative would make sense if translated "You two men!" (That's not to say there is one in Irish, only that that's how it would work in English.)
An Lon Dubh wrote:
I cannot think of an example of a noun in this declension with a strong plural that is animate however. If anybody has any suggestions.
Learning Irish gives
a rifíneachaí ! "(You) ruffians!" and
a rifíneachaí bradacha ! "(You) thieving ruffians!" (but Connemara Irish uses "strong" plural endings more than other dialects, I suppose?

)