Warrior - Ravana
Simple. Face to face combatants that value strength (Both physical and strength of will)

Paladin - Alexander
I tend to view Alex as a protector. A literal walking fortress. Even in XIV he's protecting the realm by [Spoilers]

Monk - Sephirot or Tsukuyomi
The former because I recall being punched in the face a bunch by him...
The latter because there's that balance of light and dark thing which works with the two sects of the Brotherhood and the different Chakras.

Dragoon - Bahamut
The DRAGON SLAYER job and the "King of Dragons" uhh... Right? Technically you could also say Nidhogg but whatever, Bahamut > All.

Bard - Susano or Suzaku
Lord of the Revel is fitting for BRD, whom when they're not bolstering their allies in battle are putting on a performance.

White Mage - Lakshmi
Not evil corrupted Lakshmi, but the real one, the benevolent goddess that sheltered her followers from harm.

Black Mage - Ifrit
Make everything = fire.

Summoner - Ultima Weapon?
I guess? As it's powered by multiple primals?

Scholar - Titania
Because Pixies are almost Faries right?

Ninja - Leviathan
Leviathan lives in the dark depths of the ocean, keeping out of sight. Much like a Ninja. When faced with a threat, he uses the water to attack from multiple angles. Much like a Ninja.

Dork Knight - Odin
Fell Knight clad in all black makes some sense for DRK.

Astrologian - Kinko
I mean, it makes sense right? Given how she reacted when you [Spoilers] during the [Spoilers]

Machinist - Omega?
Does the ultimate in combat technology count as a "Summon"?

Samurai - Shinryu?
I dunno... Maybe just because we see Shinryu summoned to right an injustice kind of like during the job quests when you [Spoilers]

Red Mage - Sophia
Sophia likes balance and equilibrium. So does Red Mage like to balance White and Black.

Blue Mage - Enkidu
Because, like BLU, the incarnation here is a joke.