Courtesy of reddit:
Dangolian [score hidden] 2 hours ago
"We put BLM in as a limited job because they usually exploit elemental weaknesses, but we don't have elemental weaknesses in the main game and we decided it would be better suited for solo content; no one wants a BLM that can't exploit weaknesses! Also, BLM use all their MP up so quickly in other final fantasy games casting their big spells, and we want to stay true to that fantasy, so they couldn't work unless we gave them infinite MP in some way, but that's not what people want when they play BLM."
"We have decided to make BRD a limited job. How is Bard ever going to gain levels when it does such low damage and healing ?!? We don't want to compromise the fantasy of being a BRD, but we feel it would be too weak to level solo or in a party; look at Edward in Final Fantasy IV! No one would choose him for their party at the end of the game unless they were forced to. We have decided BRD is best implemented as a Role-play job that let's you play different instruments in the city areas, and you gain experience from reactions to your performs. We will also add solo instance where you can perform for NPC crowds for greater rewards."
"Summons in final fantasy games kill enemies very quickly, so we think Summoner is too imbalanced to fit in with the other jobs in the game. Can you imagine being able to summon Odin in a raid and one shot a boss?!? It might be fun, but it will ruin the game for everyone else. There's also going to be a strongest summon, so people won't be able to choose their favourite, and might get kicked from parties if they are don't have the best summons yet. On the other side, can you imagine letting summoners into a roulette party when they can only summon carbuncle to cast Ruby Light?!? After careful consideration we have decided that Summoner won't fit group content well, and that it would be best to make it a limited job."
"After meditating long and hard, we concluded that Monk would be too imbalanced if we were implement it into the game a normal job. The job has strong Self healing skills like Chakra that don't use MP, and it also has naturally high HP and physical defence, and the ability to counter attack all incoming physical damage. We feel that Monk has to be the target of many attacks in order to deploy their counter attacks effectively, which would mean they need to be the tank role, but their usefulness against a magic caster will be much lower than an enemy who uses physical attacks. Monk would drastically limit the combat design if we made it a normal tank, so we are going to make Monk into a limited job where it can counterattack and heal through it's own solo content."
"Dragoon is going to be introduced as a limited job. We thought about implementing it a 'normal' job at one meeting, but decided against this because there is no good way to implement jump moves into standard battles. Jump attacks are meant to make the Dragoon evade all incoming damage, and deal high damage in return. This is a crucial part of the Job's fantasy, but being able to use jumps to be invincible for extended periods of time poses too much of a challenge to encounter design, so we are giving Dragoon it's own encounters where they can deploy their jump techniques to the fullest."
"Astrologian's most unique skill in it's previous final fantasy appearances was an unavoidable cast of Stop and Slow on all enemies within a large area of effect. This was obviously way too strong to allow into current content, but it's also the only skill that really defines Astrologian. As such, we will not allow the Job into any content from the past 4 years, and have set up some Astrologian-only instances so you can still use Galaxy Stop/Celestial Stasis on some enemies to feel like you aren't missing out on content at the expense of preserving the fantasy of a job that appeared for a single battle in Final Fantasy Tactics"