If anything, I would recommend just using Mooglebox to read up on each class/job's abilities/traits. It should give you a decent idea of what they do.
GLA/PLD: tank (better at tanking a single-target)
MRD/WAR: tank/melee (better at tanking multiple targets)
PGL/MNK: melee (some MP management, great at single-targets)
LNC/DRG: melee (some self hate control)
ARC/BRD: ranged melee/support (good at aoe)
THM/BLM: mage (glass cannon, great at aoe)
CNJ/WHM: healer
(Bard is pretty much just a Ranger that has to keep an eye on keeping songs on people.)
I could be horribly wrong, as I was never a Corsair and I find Archer incredibly annoying to play ever since WS began to reset Light Shot recast.
However, from my understanding their similarities are that they both do AoE buffs centered on themselves and are left with enough time to put their bows/guns to work on the boss.
In addition to Mioko's list I'd also say: MNK:ST::DRG:MT being that Dragoon shines more on Multiple Targets as opposed to the Single Target, but Dragoon is also made out of paper whereas I find a Monk can take a few whacks a Dragoon will get his face arranged real quicklike if he doesn't keep an eye on his hate-o-meter.
I'd also argue that BLM is just as viable at single-target dmg as it is at AoE-dmg with the whole Thunder/Thundara hooplah (I believe there's a video somewhere of Kaeko's LS doing MM with strictly BLMs as opposed to MNKs, for example)
I'm also incredibly biased towards Dragoons and Mages for some reason I could never tell you
So then, what is the class of the DD jobs?
PGL/MNK, LNC/DRG (needs the most work to be competitive from my understanding) are your physical DDs. THM/BLM is a great magical DD, probably the strongest job in the game. It's been awhile since I tried to use MRD/WAR as a DD only so I can't say how well it does there.
Like Mioko's list points out they're all fairly useful, but in different ways, excluding PLD & WHM. A Paladin could never really do much more than tank imo, and a White Mage could never push enough DPS to justify focusing on that instead of healing for the duration of the fight. (Though a White Mage who can smartly utilize Stone/Aero when Heals are not an issue will obviously speed up a fight, but if you didn't need the heals at some point, why have a WHM anyway is my point)
A Warrior does decent damage and excels specifically at AoE damage and has the benefit of high survivability, so much so it can function as a tank.
A Dragoon does fantastic AoE damage and decent single target damage should it be geared and played proper, but has a much higher margin of error and I imagine if sneezed on, would die. (Power Surge's need for 30 WS/Jump to reach maximum atk+ also hinders the ability to just swap&go, I feel)
A Bard can do decent damage either AoE or single target, but it's big draws are it's buffs and ranged capabilities. If you can have a DD in the thick of it, there are better options. However, only a Bard can boost your party's TP regen, MP regen, or accuracy. Battle Voice (15min ability) and its ability to further the MP/TP regen & accuracy increase and boosting your HP is p. nifty in a pinch too.
A Monk is almost strictly single target damage from the way I understand it, the ability to switch from physical to elemental damage via Fists of Element is helpful (i.e. exploiting Miser's Fire weakness or Ifrit's wind weakness) however they lack a multitude of AoE damage (I think only Aura Pulse?) and have to rely on MP for their Fist abilities.
A Black Mage plays exactly how I imagine you would expect it to be? For single target you normally use the Thunder-line which rewards Critical damage more, and AoE damage you use the Fire-line of spells. Blizzard spells are crowd-control, with the single target Blizzard inflicting Heavy and the multi-target Blizzara inflicting Bind. Also has access to single target Sleep and AoE Sleepga (compare to WHM's AoE Stonera/Heavy and single-target Repose/Sleep).
Everything I said could be wrong, but this is my impression from the few forays I've had into Primals/Dungeons.
I haven't tried using WAR in a DD-only role but I don't see how it could hold a candle to MNK or DRG.
I don't know how potent Berserk is but seeing as it resets every time you take damage it's kind of a shitty mechanic for a melee DDing inside AoE range, nvm that so many fights have adds that will be hitting people at random, nvm nvm that as a WAR you'd be expected to voke/collusion said adds occasionally to help keep them off support.
Yeah the Berserk mechanic drives me nuts considering every fucking monster has AoE and hinders WARs DD only potential, but this isn't the right thread for that discussion.
Archer is the equivalent of Ranger, however it becomes a support job when you unlock Bard. You don't have to play Bard and can stay on Archer, but the support piece is pretty amazing. You sing a song once every 3minutes and shoot the rest of the time just like an Archer. It's quite powerful.
Comparing BRD and COR isn't quiet a fair example, BRD in XIV is like a watered down version of both RNG and COR. BLM is pretty much the DD class atm, and can/will be used in pretty much every end game event. The melee jobs atm are still pretty niche, but i find them to be a bit more fun to play then BLM.
The issue is that they lose out on a lot of amazing buff abilities and there's no auto-attack so they lose out on DPS because of animation lock and the occasional delays on the timers. I love Bard, but they do need a more DD focused job branching off archer.
Edit: After re-reading your comment, I realized i'm fucking retarded. Either way they should give Archer a DD Job identity, or at least make some class AF to set it apart from Bard.
BRD has auto-attack bro. It punches w/o any input.
It has class-specific gear (Gryphonskin) stuff. The whole set with just single melds can get you to stat caps fairly easily too so it's a joke being so powerful. Archer is still really great as is and wrecks face, but when songs are so good, it's hard to say one should stay on Archer to get access to 4-5 DPS abilities (only one of which is really amazing anyway), and not change to BRD to help everyone.
BRD is pretty damn good and far better conceptualized here than in XI. BRD in XI = 0 DPS. In XIV, BRD is 50-70 DPS and provides accuracy/mp refresh/or regain effect in XI terms. It's really indispensible. I know you're not arguing that, just providing perspective. (P.S. BRD AF is also cool looking).
Meh, I guess I'll try to roll BLM. Taking a damn long time to install this game. Do I get to choose which server I want or do you guys know?