Need help deciding on class/job

[Tigore]

I will try my best to answer the questions first.

1. All the classes have their specific gimmicks to master in order to push their performance high. Although I would probably suggest the classes Rogue / Ninja and Red Mage. Both of them are more minimal on positional requirements. Their rotations generally allow you to get out of fire without losing too much DPS as well.
2. As long as you know how to stagger your defensive cooldowns and use AoEs to hold multiple enemies, it is okay to start tanking first. Make sure you have the role skills Rampart, Provoke, and Convalescence ready as soon as you can.
3. Generally the Monk is more complex to master on the rotation. You use attacks to generate self buffs and you have to be properly at the enemy flanks and rear areas to inflict the most damage depending on the spell used.
4. The Bard will most definitely be desired the most out of the four due to very high utility offered. The DPS will be a bit lower being support though. The other 3 classes you listed I haven't yet read much agreement from other players if they have something special. Just some whispers that Bards love Dragoons for the Pierce Debuff on enemies.
5. The classes that offer a balance of good utility with good DPS are usually Ninja (Trick Attack and threat control abilities) and Red Mage (minor heals and Embolden). Bard is more heavier on the end of high utility.

Much of what I said is more applicable towards what I hear in Savage Mode raids. All the classes are viable for normal dungeons and expert roulette (which are usually the 2 newest level capped normal dungeons).