Square did a good job of making thee Summoner it's own job in this game the Arcanist uses channeling magic to summon Carbuncle and Topaz and the the Summoner merely enhances the Arcanist channeling magic. That's the problem the Summoner as a job stone transforms the base class it's attached to into a powerful Mage wielding massive amount of Summoning Magic not an extension of a dot class.