Here's my opinion of various classes in Vanguard. I didn't play every class/race combo (obviously).
Sorcerers
This class still feels a little overpowered. Pretty much any race possible is fine with these guys. You'll want to put points into wisdom, intelligence, and endurance essentially. Endurance becomes extremely important as it's a relatively small pool and many spells depend on it later on.
NUKE NUKE NUKE THE NASTY MOBS! This class has the best nukes in the game, as they should. They also have extremely (overpowered) AoE spells. I've found that I can kill 3-6 mobs more easily with AoE than I can a single mob without it (at times). You can kill as many mobs with AoE as you want, as long as you can withstand the hits from them. The AoE is an instant cast, so no worries about spell interruption. (Stuns on the other hand...)
Essentially this class is good for solo, and will be great for fast group leveling especially with fellowship. The only difficult part will be finding enough linked mobs to AoE.
In PvP this class will pretty much own. Melee attacking you? AE them to death, plus your self buff has a decent low % chance of stunning your attacker. Ranged attacker on you? You have multiple instant casts that nuke + neg. affect. One is even a low DoT.
LOW LEVEL: Very easy to level up with this class, not too squishy.
NECROMANCER: Disappointed. Very very disappointed. I won't be playing this class on release, and necro is one of my fav. classes to play. The pets are pretty much sucky. The dps is low and shitty. You've got a wide variety of DoTs, but ...they're meh.
Basically a necromancer (IMHO) should have the spell range that this class currently has...if the pet is MUCH stronger. The abomination can tank pretty well (shouldn't die on you) but it can't hold agro for shit. Meaning that pretty quickly that mob will be on you. Sure you can snare and run around, or fear kite...but it's rather lame. The dps on your pet is shitty as well.
Lifetaps are meh. Basically this is a (very) slow leveler solo, and an okay grouping class. There's ghetto (very ghetto) mez, which helps in groups. The DoTs are useful on mobs that take a bit to kill. But really what kills you is that the shaman does everything you can do (minus mez) a hell of a lot better, and they're healers.
This class needs additional work that I'm not confident they'll get before release. I'm not saying don't play this class, or that it's unplayable. Neither is true. I just found that if you like healers + necro stuff...the shaman was better. The necro pets do get better at higher levels, if you stick with it.
Shaman One of my favorite classes in Vanguard. You can heal you can DoT, you can nuke, and you can wear medium armor. You can melee relatively decently. It's a fantastic all around class. You also get Call of Hero for dungeons (if the player is in range...which means pretty close to the dungeon).
They're medium-hard to level at low levels, but if you quest it's not that hard to solo them up. By the time you get your focus (at around level 15 I forget the exact level, you choose a focus, meaning bear, wolf or phoenix). Here's my understanding of the focus.
Phoenix (I've played it): You get a phoenix pet (high dps/low hp) which is an okay pet. Or you can become a phoenix yourself for additional bonuses. (Which is what I usually do). You can fly...which means you don't take fall damage, and you slowly go down from higher points. You can't fly 'up' though. You can get pretty high up if you launch from various places and travel. You can't attack things if you're not in range though. The bonus spell you get with this class is a direct damage fireball which has a long range to it. Very nice. Many players think this is the 'e-peen' focus since it's basically a 'battle shaman' focus.
Wolf (didn't play, talked to many): This is the must-go focus for healers. You can turn into a wolf, you get much faster travel speed, and you can stealth. Obviously the huge bonus here is on group/raid corpse runs. You can rez more easily if you sneak down and drag. Wolf pet is a mediocre pet and I never saw people using them.
Bear: Pet is low dmg/high hps, good taunt. Everyone considered this the shitty focus, and I only met one player who went with it. It basically makes you more survivable and the spells work accordingly AFAIK. Didn't play it, wouldn't consider it.
The one thing about focus is that no matter what people went with, they loved what they had. That tells me it's pretty balanced.
I think for long term healers, wolf is the way to go. IMHO.
Healing...you're not the best healer, and certainly not the best buffer. You're a good healer though and can be the sole healer for a group without much problem. The expertise lies in being able to debuff and DoT mobs. If there's another healer in the group (cleric or blood mage) then IMO shaman goes to back up healer. Cleric should always be the primary healer if they're present.
Solo play at higher levels becomes easier, but shaman probably do best in group and duo situations.
ROGUE They seem to have done okay with this class. This is not a class I usually play so my opinion on it shouldn't really matter honestly. They seemed okay, but I didn't like the chaining you have to do to fight. I'm lazy and I don't really like combat chains.
Rogue poison was broken the entire time I played. Stealth worked okay, but you could not stealth from other players, which I hope they maintain in PvP (primarily because cheat progs pop it anyway, so why not put everyone on an even footing). Normal stealth is harder to see, and so gives a slight advantage in PvP anyway. Rogue combat chains do nasty dmg, and they're good DPS.
It's not a brainless class, and that's good. There will be no 'one button' rogues in the game. And they weren't highly common because again, requires some skill and attention to playing.
Not a class I'd play, but that's personal preference not because it sucks or anything.
PSI: This is basically an enchanter. They're beyond squishy at low levels. Very hard to level up solo...which is good. This isn't a solo class IMO. They're the best crowd control, and highly desireable in groups. Their dps was higher than my necros at higher levels.
I didn't play one to a high level (I think to like 12) so my opinion is based on people I played with. It's a good duo class, and a skill class (meaning you need skill to play it well IMO). EQ enchanters will find it familiar, and there's buffs similar to KEI. Very nice buffage, and an essential group class at various points.
BARD I never played this class, and wouldn't want to (personal preference) but I played with good bards off and on. They're the best pullers, and a tremendous class to have in group with you IF PLAYED WELL. A shitty bard is worse than useless.
Good dps with the right gear, best pullers I saw in the game, so-so crowd control (good when played well if only 1 add mob) and jesus pullers I mean just jesus.
I'll take a good bard in a group I'm in over any other class.
DISCIPLE I played this and didn't like it so dumped it pretty low level. They're good healers, they're kinda like a monk/healer combo. They have heal chains though that when built up over time are ungodly good. Eventually it causes so much hate they can't lose agro. They seemed a good backup healer, as they have to fight to do their heals as well. A good overall addition to the group, but not essential (but a good backup healer when played well).
Requires a lot of skill and paying attention to chains.
MONK Never played and what little I saw didn't impress me. Not a commonly played class which tells you something.
Druid Played after the revamp and it sucked so badly I dumped it. Only spell I had was a damage snare which was less than useless and my dps was shit. This class sucked donkey balls. Maybe it's improved, but I thought it blew.
Blood Mage: Caster/healer class (cloth). this is actually a decent class, but I didn't really like it personally. They're good healers though and most people who played them loved them. I can't put my finger on what I didn't like about it. Maybe because really the casting was kinda meh, it's cloth and I felt that shaman/cleric could do things better.
Seemed highly popular at one point when broken because you could essentially kill anything and not run out of mana/healing. That was fixed. They're a good healer because they're very mana efficient but being a cloth class, have to watch agro.
Worth trying if it appeals to you. I don't know enough about it to give a good overall other than, if you want to be a cloth caster with good heals, try it. highly desirable in groups because of healing efficiency.
RANGER Didn't play. Had good dps at one point then got kinda gimped. Very good with bow, decent buffs too. Medium armor IIRC only. With bow they seem to be pretty efficient in PvP from what I saw, lying on the ground...dead.
If you like EQ rangers you'll prolly like this class. Doesn't appeal to me so I don't know much about it. Only grouped with crappy ones, so they didn't impress me, but heard they can be very good.
TANK CLASSES
Didn't group with them much and they seemed to be broken (or not in the game) quite a bit. YMMV.
Cleric Seemed impressive, but that was due to Grimmier, who is IMHO a very good cleric. I had one but never played it really. The shaman appealed to me far more as it combined the 'best' of cleric + necro for me.
They can wear heavy armor, so-so dps, they can take hits. Best buffage (so it seemed) among healers, cons being not the most mana efficient healer. Good primary healer, probably best primary healer.
So that's it. =)