Picking what class to play is one of the first choices you make when considering a build, so it's important to understand what makes each class unique. This article will go over what each class offers the group in Group PVE Content. There's plenty of other differences that matter in other contexts, so this is far from an exhaustive list.

Dragonknight

• Excellent tanking passives. Combustion + Helping Hands gives great stamina sustain while blocking, making it really easy to permablock.
• Unique tank utility skills. Relentless Grip was the only pull skill that cost Magicka for the longest time, and even now it still has the benefit of only using the Magicka if the pull is successful. Magma Shell is a unique form of damage mitigation that allows you to survive almost anything in the game. Protective Plate gives a flat 50% damage reduction to projectiles which can be useful in niche situations. Igneous Shield can proc your Helping Hands passive while also giving damage shield to the entire team. Igneous Weapons allows your team to use tri-pots and still get the damage buffs they need.
• Unique debuff of Stagger through the Stone Fist skill. This alone makes one Dragonknight mandatory on an optimized roster.

Sorcerer

• Somewhat unique buff with the Storm Atronach ultimate. Very useful in a team composition.
• Best block mitigation in the entire game with Bound Aegis. This allows Sorcerer tanks to survive against damage that most other tanks would fold to.

Templar

• Best purge in the game with Extended Ritual. Assuming your team hits the synergy, it's a free purge for everyone. It's also a great skill to help your teammate wearing Alkosh as it's a guaranteed synergy they will get every 20 seconds.
• Highest execute damage in the game with Radiant Oppression. This is offset with a mediocre amount of DPS prior to execute. 

Nightblade

• Great healing output with their class heals.
• Somewhat unique debuffs of Major and Minor Cowardice, providing a lot of damage mitigation to the group.
• Highest passive ultimate generation out of all of the classes as they have two passives that provide ultimate.

Warden

• Great healing output with their class heals.
• Unique buff of Minor Toughness makes at least one Warden mandatory in any team composition.
• Unique group utility skills. Frost Cloak gives Major Resolve to the entire group, saving tanks a skill slot and increasing survivability of DPS. Shimmering Shield can absorb most projectiles and generate a lot of ultimate. Frozen Gate can pull a lot of adds at once which has niche use in trials.
• Unique DPS setup built around the passives in the Winter's Embrace tree. Provides high uptime of minor brittle.

Necromancer

• Somewhat unique debuff of Major Vulnerability with their ultimate Colossus. This makes having at least one in a team composition very useful.
• Ridiculous ultimate generation in trash. Necrotic Potency can generate up to 60 ultimate in one trash pull. Combined with their ultimate this means you can have a very strong debuff applied very frequently.
• Strong tanking passives. Disdain Harm gives 15% damage reduction to DOTs, making Necromancers extremely good tanks in cases where there is a lot of incoming DOT damage.
• Great utility skills. Boneyard is AOE Major breach and provides a strong synergy. Agony Totem gives the group Minor Protection and the enemies Major Cowardice. Reanimate is a very potent ultimate in progression groups as you can revive a quarter of the group without having to stop whatever you're currently doing.

Arcanist

• Best AOE damage in the game with Fatecarver. Very easy to use skill.
• Provides a lot of unique or hard to get group buffs. Zena's gives the group Minor Courage, Circumvented Fate gives Minor Evasion, Rune of the Colorless Pool gives Minor Vulnerability and Minor Brittle to one target. There's also a unique Weapon/Spell Damage buff from the Glyphic ultimate.