There was a bit of misinformation in this post. I haven't played seriously in a few years but played at a very high level at points in the past. Here's a more accurate version:
If you'd like more information about a class or how it plays in RVR, PVE, etc, feel free to ask.
Armsman: Good tank in PVE, typically plays either a "peeler" or a dps role in RVR groups. A peel tank's role is to counter the enemy tank train: they guard the enemy tanks's targets, stun enemy tanks with shield styles, and use melee snare styles on them to keep them from reaching their targets.
Cabalist: Pet caster, popular in PVE. Can spec for AE dots (nasty with wild arcana in keep sieges where people won't consistently receive heals) in the matter line, but nobody that plays 8v8 RVR uses that build.
The strengths of this class in 8v8 are: nearsight, disease, a debuff that improves the damage of the main nuke used in the realm, solid pet. The only potential issue is that without access to the mastery of focus realm ability, spells may resist quite a bit due to being lower level. Might not get consistent pick up groups.
Cleric: Main healer/buffer class. Good class to play if you enjoy healing and want to find groups easily.
Friar: Healing / melee hybrid. Good in PVE, the resist buffs are useful in RVR, has a really solid snare style in staff spec. But won't get many groups unless you're amazing, charismatic, or have a set group with friends. Can heal decently but is countered by nearsight.
Infiltrator: Assassin for albion, can stealth. Typically played solo or grouped with other rogues in RVR, most serious (non stealth)players won't group with one. Really strong in this patch level at low realm rank. Solid dps in PVE.
Mercenary: Light tank of albion. Sort of like an EQ rogue or monk. They do great damage and have the ability to throw dirt in an enemy melee character's eyes, increasing their miss rate. Really popular class, great in PVE and RVR. Should have no problem finding a group as a mercenary.
Minstrel: Music class in albion. Really powerful if you know how to play it well, but difficult to master. They are similar to a bard in EQ (best speed buff, can charm)with a smaller range of abilities. They have one of the strongest realm abilities in this period. Desired in every situation typically.
Necromancer: Amazing group or solo PVE class. Bad in solo RVR, can work in one specific RVR group but
nobody will group with in RVR unless they decided that they would from the start. The necromancer summons an undead pet, then becomes an invulnerable ghost (shade). The player can cast a few low range spells as the shade, but the majority of time is spent controlling the pet.
Paladin: A cross between an EQ bard and a warrior. They get access to short duration chants that buff their party. One of the buffs is an endurance regeneration, but the range is pretty low at this patch level, and without determination, they'll be stuck in crowd control for the majority of fights. They can tank well in PVE, really popular there. Probably won't get groups in RVR unless you have friends.
Reaver: "evil" paladin. Cool class, has a series of pulsing pbae debuff auras and their melee styles are really unique (some have spell procs added, one has increased range). Unfortunately, because they lack determination, nobody is going to pick one up for an RVR group. They were semi-viable on the old version of Uthgard with new realm abilities, but not really optimal here. Good PVE class, can be high DPS if their style procs land.
Scout: Albion's archer class, has access to stealth. At this patch level, assassins will be able to detect archers from quite far away. So it's probably best to play one of these in RVR with some infiltrator friends. Archery could never miss in PVE on the previous iteration of the server so they were good in PVE. Won't be invited to serious (visible) RVR groups.
Scouts were traditionally the strongest archer because they had access to shield slam, but due to the ruleset on Uthgard, they're probably the weakest. They lack the self buffs that other realms archers receive and do low melee damage.
Sorcerer: Similar to an enchanter from EQ. Access to a lot of debuffs, crowd control abilities, charm, and a few nukes. Good in group PVE and RVR, very boring to play on raids. Easy to find groups with.
Theurgist: Summons short duration elemental pets that attack your target. Useful for interrupting enemy casters in RVR and breaking to-hit code (if enough attackers are fighting a boss, it becomes significantly easily to land attacks on them) in PVE. Theurgists also have access to PBT which is desired in groups. It's an aura that blocks a melee attack every few seconds.
Wizard: One dimensional DPS caster, won't really receive 8v8 groups. They're solid in PVE and keep defense with the ice spec line.
Animist: Sets ground targets to summon stationary mushroom turrets. Really strong in PVE for the same reason the theurgist is. They are super strong in keep sieges, okay in open field RVR, but people probably won't invite you to 8v8 groups unless you're pretty good or their friend.
Bard: Music class for Hibernia. Main crowd controller for the realm that provides speed and endurance regeneration. Popular class, easy to find groups, but people will probably want you to lead the group in RVR, which may prove to be daunting to newer players.
Blademaster: Similar to mercenary for Hibernia.
Champion: A hybrid melee and debuffer. They have access to really strong debuff abilities, but, like the reaver and paladin, lack the determination realm ability, so most people aren't going to group you.
Druid: Like a cleric, but have access to a pet. Highly desired in groups.
Eldritch: Somewhat similar to a cabalist without a pet. They have nearsight, high damage nukes, disease, debuffs (no relevant resist debuff unless you're grouping with an animist). Popular class in RVR (light for 8v8, mana for keep sieges) and PVE (when mana specced). They're boring to play on raids.
Enchanter: Popular class in PVE. Pet caster with high damage nukes, but not much utility. They're famous for their resist debuff (heat) that matches the resist type of their stun and single target nuke. You will likely be able to find RVR groups as an enchanter, but they aren't as popular as eldritches.
Hero: Similar to armsman in Albion. Can transform into a weird stag thing for an hp boost. Main tank in PVE. Popular in RVR.
Mentalist: Interesting class but not as popular as the other two casters. In PVE you have the only usable HoT in the game and mana regeneration, so they're great in that regard. In RVR they have access to high damage heat based nukes that synergize with the enchanter debuff, cure mez, small heals, and a pulsing charm spell that can be used to break mezzes and roots on yourself. They're great in keep sieges because they can spec into AE dots like cabalists can.
Nightshade: Hibernian assassin, has access to an instant cast nuke on a timer and a casted nuke. They're probably the best assassin at high realm ranks with everything up.
Ranger: Archer class with a self buff line.
Valewalker: Caster / melee hybrid class. Doesn't nuke as hard as a caster, and lacks determination so they aren't amazing as melee DPS either. However, they're quite strong in solo RVR, and probably decent in PVE. They get to use cool scythes too.
Warden: Secondary healer and base buffer in Hibernia. Has access to pbt. Mostly heals people, snares tanks, and interrupts enemy casters in RVR. Popular in PVE, but not every RVR group wants to run one.
Bonedancer: Pet caster with a commander pet and up to three AI controlled sub pets. The sub pets have differing roles based on your spec: they can be mages, healers, buffers, archers, etc. Most known for having an instant cast lifetap on a 4 second timer. Grouping as a BD will be similar to a mentalist on Hibernia. You're not a weak class, but there are only 8 spots and you don't really have anything that stands out in 8v8.
Healer: Main crowd control and healing class in Midgard. Has access to base buffs only. Really powerful class, fun to play, but difficult to play well. Easy to find groups on.
Hunter: Archer class with a pet, the ability to charm animals and some buffs.
Runemaster: DPS caster with access to nearsight and PBT.
Savage: High DPS melee class with short duration self-buffs that cost hit points instead of mana. Can use hand to hand weapons and potentially hit four times per round. They can put out great damage if you get lucky with swings, but can't get PF so they're not as useful as berserkers during this period.
Shadowblade: Were nerfed right before the patch Uthgard is based on. Somewhat weaker than other realms' stealthers, but can compete if you're a solid player.
Shaman: Main buffing class for Midgard. Primarily interrupts people in RVR. Popular in groups.
Skald: Midgard music class. They primarily use two handed weapons and have access to some utility chants, crowd control, and damage shouts. They're okay at this point, but due to group limitations they aren't super popular in high level RVR.
Spiritmaster: Pet caster in Midgard. Known for PBAE (for keep defense and leveling), a pet that can absorb melee swings directed at you if you're close to it, and debuffs. Again, somewhat similar to a mentalist, where you won't get consistent RVR groups.
Thane: Like a valewalker but uses chain armor. Their nukes aren't very strong, no determination. They were solid PVE tanks on the last iteration of Uthgard, but that involved an RA that no longer exists.
Warrior: Armsman / hero of Midgard.
Berserker: Mercenary / blademaster of Midgard, doesn't have access to shields, though.