I've had a few friends wanting to try out the game recently and asking me what to play. As a leader of a guild it's my job to at least pretend to know something about all the classes. Here is my insight on how I think the current state of the 12 AoC classes are as of the beginning of June, 2008. Please take these with a grain of salt as I'm just trying to give a rough overview and not a detailed look into each class.
PVE: A great tank. Highest Hit Points and armor makes them the ideal choice for any PVE group. They, along with the Dark Templar, are the only really viable "Tanks" in the game. Can solo pretty well with not much downtime.
PVP: A beast against any melee class and strong against casters as well. Currently, they actually do more damage specced sword / shield, so those wanting a 2 hand polearm build are going to have to wait until it's fixed. They can do some incredible burst damage and take forever to kill.
PVE: Wonderful to have in the group, if for no other reason than their in combat res. They can't tank as well as a DT / Guardian, but they still have high HP / Mitigation and taunt skills so they make a good offtank. It's better to have one of them tanking than a squishy. Can solo ok - nothing great - with little downtime.
PVP: A great support class to have in a group mainly for their auras and combat res. Their damage and survivability isn't bad, but nothing spectacular. Using two handers, they do more burst than Dark Templars (and sometimes Guardians). They also have a lot of knockdowns so are good to protect the casters. Not a great solo PVP class.
PVE: Lowest Hit Points out of the 3 Soldiers, but can still tank very well. Needs to micromanage a lot of skills to tank properly and use life drains. Best at tanking groups of stuff but still good with single target tanking. Can solo with virtually no downtime and handle huge groups of mobs at a time.
PVP: Low burst damage, high survivability. Most melee classes you'll just laugh off. You'll have a tough time killing Healers and an easier time killing Mages and Rogues. Good in groups as you bring quite a few group drains and abilities.
PVE: By far the worst Rogue class for solo PVE. Does extremely high damage but can take very little punishment, making this an ideal grouping class. Have a few lifesaving abilities on cooldowns, but very little mitigation and hit points. Almost impossible to kill groups of mobs unless they are way lower than you. Can duo fairly well with a class that can survive.
PVP: Does the least amount of sheer burst damage of the Rogue classes which is strange. Can sometimes take out single targets (depending on armor / hit points) but more often than not ends up short. Nearly impossible to take out healers with as they can outheal your damage if you don't kill them with your first (and only) knockdown / CC. A good group PVP class that is nearly unstoppable with another rogue class taking the same target.
PVE: High damage, high hit points, low armor. You do a ton of damage and have some nifty knockdowns to go with it. Not a great solo class, but your AOE abilities and high hit points allows you to take out groups of mobs quickly or down single targets fast. Along with the Assassin, a great melee DPS to have in a group. Great class to duo with a healer or soldier.
PVP: You can take almost any non-Soldier class out before they can do anything. Using all of your knockdowns and CC, you can do enormous amounts of damage before anyone can react. After these are gone you're extremely vulnerable. Very hard to play against Soldier classes as they will survive this initial attack.
PVE: Great at single / double target PVE soloing. Has trouble with groups of mobs. Good in a group as you provide steady ranged damage. No group buffs to bring to the party.
PVP: You can do high amounts of damage in a very short period. 20yard range makes you a hybrid ranged / melee character. You can perform well against squishy targets but have trouble against the Soldier archetypes.
Herald of Xolti
PVE: Extremely squishy - low hit points - low armor. You kick out a lot of damage. A bit tough to solo with as your survivability is low but you do good AOE damage. Good in groups or duoing with another class.
PVP: Your Fire Lance + root / mez will be able to take some people out in one hit. Survivability is your main concern. Can be a frustrating class to play in solo PVP but does well in group PVP. Gets a charge like ability + some self mitigation spells that are a bit hard to keep up all the time.
PVE: Broken class past level 50. Does piss for damage. Spells and abilities are broken and don't scale well if at all. Pets are a nightmare to manage. Class review hopefully coming soon.
PVP: Pretty much a free kill for everyone. Low hit points, low damage, low armor / survivability. Your nukes can't even scratch a healer with a single hot on them. Life isn't good.
PVE: Gets progressively harder to level with past level 30. Spells scale poorly and some abilities / talents are not working. AOE damage is ok but has been nerfed recently. Currently bugged in groups and usually pulls huge amounts of aggro for no apparent reason.
PVP: Another free kill class. No survivability, low damage and hit points. Can get lucky and kill some melee classes from ranged. Class review also coming soon.
PVE: Does fairly good solo with absolutely no downtime. Moderate AOE abilities but very low hit points. Needs lots of micromanagement to be played properly. Wonderful group class with an emphasis on melee support. No group buffs but has the most Heal over Time spells of any healer. (short range on most of them)
PVP: Suffers from low hit points but can last virtually forever if you don't kill one in the first 10 seconds. Has a knockdown plus short duration stun + 2 snare abilities. Heals are centered around caster, needs to be in melee to heal effectively. Gets a lot of self buffs and a few party abilities like remove root. Can spec to get charge like a Soldier. Not a bad solo PVP class but best in groups.
Tempest of Set
PVE: A juggernaut of AOE killing. Can take groups of 8+ even level with virtually no downtime. Great solo class + in groups. Brings hit point buff + electrical damage to the group along with good healing ability.
PVP: Good survivability and good damage. A very good solo PVP class and also great in groups. Can be devastating if left alone in a battle. Usually a priority target in PVP (along with the other healers). Gets a root, snare + a knockdown at high levels.
Priest of Mitra
PVE: Highly sought after in PVE groups. Regarded as the best healer. Also extremely effective in PVE aoeing. Not as good as the ToS, but can still do good solo. Has a group HP buff along with lots of other goodies.
PVP: A beast of a class in PVP. Has almost countless CC abilities, good survivability. Damage isn't great but can still be enough to kill any other class that can't heal. Damage is mainly PBAOE focused with the ability to do moderate direct damage.
--- So, think I got something wrong? Feel free to add your corrections! Always looking to gain more insight on the classes.