Posting this here from a thread I saw. This may give you a good idea of how the jobs will work at endgame. With the exception of Summoner and Scholar of course since they're not in the game yet.

Warrior - let's start with tanking. Warrior honestly is fairly basic and doesn't get much more complicated than when they started. The main reason for this is because of the new engine, they're able to implement dungeon encounters that are much more complex than before. Since the tank is almost always the one in charge of handling mechanics (dodging/stunning boss' special moves, moving the boss out of bad areas etc), the added complexity of the role comes not from the class but from the boss encounters themselves. Stunning is an almost essential part of tanking, and for that you have to watch out not only for the red aoe circles but also for long cast abilities. You also gain access to the whole defiance/wrath stacking mechanic, which is fairly simple but if you're tanking a boss, timing when to use Inner Beast and utilizing the heal effect is a nice added element.

Paladin - somewhat similar to Warrior in the sense that you're still in charge of boss mechanics and dodging/positioning but with an additional resource to worry about: mp. Unlike Warriors who can tank multiple mobs and hold aggro just by spamming Overpower, Paladins rely on Flash which is very mana-intensive. Normally this isn't an issue since normal combos have innate threat-generating quality but when it's time to tank multiple mob, you better have some spare mp. Thankfully Paladins get access to another combo that while it doesn't generate any additional threat from damage, it restores mp. And this is where Paladins have an extra mechanic to get used to, knowing when to expend and actively replenish their mp. Add to that a wide array of defensive cooldowns they get access to and it becomes more reactive and tactical that what it starts off as.

Dragoon - now I'm gonna be honest, the physical dps classes are probably the most basic ones compared to the others, but hey, that's always been the case in every MMO. I played a Hunter in WoW and it was never any more complicated than following a simple priority queue of your most powerful abilities (rotation is a common but inapt term for this priority queue of abilities). With Dragoon it's mostly a small matter of position yourself correctly to maximize the damage potential of your weaponskills. You get access to 2 main combos, the second of which is started from behind the target and used only to put up the DoT effect from Chaos Thrust, otherwise you stick to your main, more damaging combo. You do get DoT/Slow weaponskills to use when appropriate but otherwise it's just a matter of cycling through your combos and using your Jump cooldowns to maximize efficiency. Sure it's simple and if you really wanna play badly you can stick to just pressing 1,2,3. But if you're even half a decent player you'll be utilizing at least 10 keybinds not including your stun and personal buffs.

Monk - somewhat similar to Dragoon with the exception that your top priority is keeping up your Greased Lightning buff, which provide an excellent increase in damage and, unique to Monk, a fairly significant increase in Skill Speed. This means at level 50, with proper gear and full Greased Lightning buff, your global cooldown would be closer to a flat 2 seconds instead of 2.5 seconds. This may not seem much but it is very noticeable in combat. You have less time to decide what your next action will be, and since Greased Lightning wears off in just 12 seconds if not refreshed, it's top priority to be able to execute a skill that refreshes it before it runs out. That's in addition to other abilities you may want to perform outside of your normal combos, which is again, like Dragoon you get 2 main combos, which are even more demanding in terms of positioning for maximized damage.

Bard - mainly straight-forward in most cases with the exception of utilizing songs which I have to admit I haven't had the opportunity to test out in a party setting because of the lack of level 50 party content. The dps part of Bard seems very simple and doesn't change much from what it is at low levels. You don't have any combos, you do get access to 2 strong DoTs that are essential to keep up on bosses. You get Straight Shot that grants a 10% damage increase self-buff but your main weaponskill (Heavy Shot) also has a chance to proc a buff that makes the next Straight Shot a guaranteed critical hit. You want to take advantage of the proc not only to score a critical hit but to refresh the Straight Shot buff on yourself. So it boils down to a proc-based gameplay which is more reactive than a straight combo-based playstyle utilized by the other physical dps classes. The simplicity of this part will be (I'm guessing) augmented by the role that songs will play later on in end-game situations.

White Mage - people who say healing in this game is so easy and simple that Conjurers should be nuking mobs half the time to help dps simply haven't tried healing in later levels. This is the most hectic and stressful role in the game, period, even more so than tanking. Sure at lower levels you can spam heals as much as you want and then nuke when the tank is in the green. But at higher levels there's an issue: mp management. Simply put, despite getting access to different tiers of healing spells, this role is not like other MMOs where it's just a given to use the highest ranked spell you have access to. You try spamming Cure II to your heart's content? You'll be oom halfway through a boss fight. Instead SE decided to inject an element of luck to healing. Much as Bard employs a proc-based dps style, White Mage is also dependent on procs to save mp on long fights. Each lower tier of Cure spell has a chance to proc a buff that lets you cast the next Cure spell in the ladder with no mp cost. This is in addition to keeping everyone buffed up and dispelling ailments on party members. The most traditionally reactive-style of playing in MMOs just got even more reaction-based.

Black Mage - again, like Bard this is a proc-based style. In a sense this is most interesting class to play simply because there are a few different ways which it can be played. For people who don't bother looking into their abilities this would seem very simple: simply spam Fire or Fire III until your run out of mp, then switch to Blizzard/Blizzard III. For the min-maxers that have been testing the dynamics of Black Mage it's not quite so simple. You get access to tiers of Thunder spells in addition to the usual Fire/Blizzard exchange and in most cases, stacking all 3 Thunder spells provide excellent damage in addition to providing a high chance to proc (5% per tick per spell) a buff that lets you cast your next Thunder tier spell instantly and with no mp cost, plus having the normal DoT damage added to the initial damage. While your watching for that proc you can also spam your basic Fire spell for a 30% chance proc of making your next Fire III spell instant cast and cost no mp. All of this makes for a very hectic gameplay when trying to maximize your damage in addition to your usual CC duties in a party.

inteeeresting

Looks like our white mages will have to be pretty skilled

at lvl 20 some encounters already had a big mp management requirement… lower levels it was pretty easy tho.

Brds should help with mp management. They have an MP regen song.

When spamming that lvl 32 dungeon with Defiled on the last day…we realized how essential it was to have a decent tank. Out of the 8 or so times we went, we only had 1 good tank that practically never lost aggro. The rest left the adds to the healer and to the dps to tank.

I'm most likely going to be playing a healer, mostly because I actually found it kind of fun this time around when doing some dungeons.

black mage go

Hearing a lot of complaints about Bard. People are saying it's DPS is good but it's support is pretty lacking and it's the simplest class in the game to play. So I'm not sure what I'm going to play yet.

I suspect that once an expansion/major update comes out with an increase in max level that the Bard will get plenty of support and become complicated again. But I have to agree, Bard is no where near as complex as it use to be.