This profession guide is accurate as of BWE2.
Masters of mechanical mayhem, engineers tinker with explosives, gadgets, elixirs, and all manner of deployable devices. They can take control of an area by placing turrets, support their allies with alchemic weaponry, or lay waste to foes with a wide array of mines, bombs, and grenades.
-Official Guild Wars 2 Website
If the eight professions are comic book superheroes, then the engineer is Batman. Engineers get all of the cool gadgets and useful tools to get the job done. From their turrets to their kits (skills that give you a new weapon with five new skills), engineers are all about looking cool while you stomp people. Their major class mechanic, the tool belt, gives them an extra skill based on each non-elite slot skill. Essentially, engineers have four pairs of slot skills plus their elite.
Rifle – The rifle offers a lot of skills for keeping enemies away from you. Jump Shot is a targeted leap in any direction and is also handy for jump puzzles. If an enemy does somehow get close to you, Blunderbuss can make them pay at point-blank range.
Pistol (MH) – The main-hand pistol has an emphasis single-target AoE. Even its auto-attack, Explosive Shot, has a built-in AoE.
Pistol (OH) – The off-hand pistol gives engineers a little extra close-range offense, but also offers Glue Shot, one of the most powerful immobilizing skills in the game.
Shield – The engineer’s shield gives some useful defense against both melee and ranged. Static Shield can not only stun attackers, but daze far-away foes!
Harpoon Gun – Engineers sadly have only the harpoon gun for underwater combat, but it offers a good mixture between offensive and defense while giving a good amount of AoE.
Engineers have a lot of turrets, kits, and elixirs for skills, but they also have some handy gadgets. Med Kit lets you start dropping bandages for allies to pick up at will, while its tool belt companion is a straight heal for yourself. Healing Turret drops a turret that does exactly that: it heals you and then provides healing to your companions. Its companion skill will remove all conditions from nearby allies. Finally, Elixir H heals you and gives you a random buff, and its companion skill gives you an AoE with a random defensive buff as well.
Gadgets – Gadgets are little utility skills that have have largely have some form of movement control involved in most of them.
Turret – Turrets are all little devices that you plop on the ground. They sit there and attack targets in range with various effects .Every turret has some sort of overcharge ability on the toolbelt that gives a related, more powerful version of the main effect. Additionally, every turret has a toggle detonate skill that puts the turret on cooldown after the explosion. Turrets may also be picked up for a (slightly) shortened recharge.
Weapon Kit – Weapon kits give you a new weapon that takes over your main bar. Flamethrower gives a lot of burning and movement effects. Elixir Gun has a lot of AoE and condition-based combat as well as some healing and regeneration. Tool Kit gives you a lot of defensive skills as well as the ability to repair your turrets.
Device Kit – Device kits, like weapon kits, give you a new weapon bar. All three device kits are heavily based on explosions and AoE effects. Bomb Kit sets down bombs that explode after a couple seconds. Grenade Kit gives you thrown explosives that detonate on impact. Mine Kit gives you five throwable mines that detonate via remote or proximity.
Elixir – Elixirs are self-buff skills with mostly random effects. Each elixir comes with a tool belt skill that tosses the elixir creating an AoE of a similar random effect.
Elite – The engineer’s elite skills are a fun bunch that also fit the theme of the engineer’s inventiveness. Supply Crate creates a random bunch of bandages, turrets, mines, etc. at the spot which last for 60 seconds. Elixir X gives you a random form elite from the elementalist, necromancer, and warrior professions. Mortar creates a stationary mortar, lasting 120 seconds, which can rain powerful AoE blasts from a considerable distance.
The five trait lines for the engineer are named after things the engineer uses. The final line has the engineer-only attribute, Ingenuity, which reduces the recharge of tool-belt skills.
Explosives (Pow/Exp) – The minor traits create explosives conditionally and add vulnerability to explosions. The major traits add effects to explosions, cause turrets to explode on death, increase size and range on explosives, reduce bomb and grenade recharges, increase explosion damage, and cripple enemies hit below 25 percent health. The final traits are Elixir Infused Bombs and Explosive Powder.
Firearms (Pre/Mal) – The minor traits add bleeding to criticals, damage to bleeding enemies, and crit chance against low-health enemies. The major traits increase gun recharges rates and range, add boons or conditions to criticals, add cripple to immobilize effects, increase damage to immobilized enemies, make pistol shots pierce, increase rifle damage, increase harpoon gun damage, and add defensive buffs to the flamethrower. The final traits are Coated Bullets and Juggernaut.
Inventions (Tou/Com) – The minor traits give aid when under 25 percent health and buff power. The major traits buff turrets, give protection when rallying, turn you invisible when immobile, remove boon with mine explosions, add supplies to the Supply Crate, reduce damage taken, and increase movement speed in combat. The final traits are Electromagnetic Mines and Rifle Turret Barrels.
Alchemy (Vit/Con) – The minor traits give boons at 75 percent health, turn some conditions to boons, and increase damage for each boon. The major traits add a chance to poison attackers, buff condition damage, buff elixirs, give buffs to being under 25 percent health, add regeneration to kits, add vigor to swiftness, and buff the elixir gun and flamethrower. The final traits are Automated Response and H.G.H..
Tools (Pro/Ing) – The minor traits buff tool belt skills and increase damage with full endurance. The major traits increase endurance regeneration, buff kits, drop flamethrowers or elixir guns when downed, reduce gadget recharges, add vulnerability to blocks, and give turrets automatic reparing. The final traits are Armor Mods and Autotool Installation.
Engineers aren’t overly complicated, but they require finding a combination of skills that work well together and demand learning the tool belt skills in addition to the regular slot skills. For some players, the engineer will be very easy, while others will find it challenging to come up with an enjoyable style that works.