Strictly speaking, the current summoners are closer to what I see as the old Elementalist job, in that they use the elements to inflict status ailments.

Whereas Summoners themselves should be something akin to this - see the gallery at the bottom of the page. They summon spirits themselves for short periods to deal heavy directed AoE damage and have insane MP reserves. Imagine Limit Breaking a full-scale Ifrit Hellfire onto the battlefield, how awesome wouldn't that be? o_O Balancing difficulties aside, I think that's what the Summoner job should have been. Too late for that now though, they'll not rework a job that's been in play for two years.