Scholar
Pros:
-Pet (heals while in Cleric Stance)
-Powerful shields
-Strong AoE regen or Attack speed buff
-Limitless (effectively) MP
-High sustained DPS
-Emergency Tactics
-Deployment Tactics
-E4E
-Supervirus

Cons:
-Wields a book
-Lowest HPS potential

White Mage
Pros:
-Strong heals
-Free MP procs
-Cure III
-Highest AoE range
-High burst DPS

Cons:
-Poor shielding/mitigation
-Few to no support buffs

Astrologian
Pros:
-Stance Dance, strong heals / mediocre shields
-Strong RNG focused team support/buffs
-Strong aoe heals
-Most mobile healer

Cons:
-Mostly has what the other two jobs have, but slightly less + RNG focused buffs