I don't think so.
About the summoner job, it's a really good mage class, as it group-casts automatically without losing power. I've had my Yew as Summoner/Bishop all the time, and he's the ultimate mage for me. These two simply outclass the Red/Black/White mages.
I have a feeling you might know this, but these are the monsters you can summon in this game; note that if you've reached lv 11 with that job, each summon has 2 variants (one offensive, the other being a buff).
-Hresvelgr- a powerful wind attack
-Ziusudra's Sin- a powerful ice/water attack
-Deus Ex- a powerful volt attack
-Promethean Fire- a powerful fire attack
-Susano-O- a powerful dark attack
-Charybdis- an attack debuff spell, decreases all enemies' physical and magical attack to its 75% value
-Amaterasu- the ultimate healing spell- heals 9999 HP on ALL targets.
Now, why is it overpowered? If an enemy has an elemental weakness, you can use the Wizard passive that allows the use of Spellcraft, and then spam their ass with elemental rains (Hresvelgr Rain, for example). Or if an enemy is strong against magic, you can either combine the job with the Black Mage's Ignore M.Def passive, or simply use elemental hammer (Deus Ex Hammer, etc.). Also Charybdis Dart on fast, powerful bosses, and let us not forget about the glorious Amaterasu Mist, that heals the entire team to full HP for 3 turns. Oh, and the Bishop's Calm ability can deny ALL damage dealt in the turn, which, combined with Amaterasu Mist and/or Enopu Mushrooms, can turn the entire battle upside down.