Beastmaster always overlapped with Summoner from my experience; even in the single player games. You could summon monsters that were not traditionally summons like bombs, wyverns and cockatrice or however you say it. I say that because it begs the question, do we need beastmaster? I say sure.

Beastmaster always felt like Summoner to me, but a lesser version. It leads me to believe that beastmaster may function similar to the bahamut summon, instead of walking around with the pet. In that case, beastmaster could be a group job.