Engineer’s build variety is pretty much unrivalled amongst the classes. There comes a certain point in mastering any class when you realise that pretty much most skills and utilities are “worthy” of slotting on your bar. The only “bad” skills are the ones that are outclassed by other skills in the same category.
For Engineer, what you put in slots 6-9 defines how you play, unlike other classes where it is usually weapons and associated traits. Many skills and utilities are also counterintuitive when first picking them up, which doesn’t help when levelling an Engineer blind. Rifle, for example, shines most when used up close. Counterintuitively, Pistol/Shield is the mid-long range favoured weapon while Pistol/Pistol is strong at mid-short ranges.
In terms of traits, Engineer traits are a minefield of uncontested best-in-slots like Incendiary Powder or absolute bombs like Autotool Installation. On the plus side, Engineers aren’t as trait dependant as other classes unlike Mesmer, where what you trait literally defines what you should then slot best in utilities.
In terms of skill floor and skill ceiling, Engineer’s skill floor is quite high, and it is easy to feel like you do no damage or are simply outclassed in other aspects without fully exploiting the mechanics of a skill. You will not do well by auto-attacking with any weapon save for traited Grenades. Even then, there are tons of activations you can slot in between large cooldowns to boost your own damage or survivability or team support. You haven’t played engineer until you have more than 1 kit, that’s for sure.
Engineer’s also one of the few classes that boasts animation and GCD cancelling to a large degree. Before the nerf to Kit refinement, Guanglai Kangyi’s GCD cancelling Kit refinement build boasted one of the highest sustained DPS achievable to the Engineer, although you probably needed a macro mouse or inhuman APM to achieve it:
http://www.youtube.com/watch?feature=player_embedded&v=del9A5Erb40
You can also GCD and animation cancel the following:
Swap to med-kit -> Swap to weapon kit: This bypasses the 1 second kitswap requirement introduced with the Kit Refinement nerf and can even be used while autoattacking. Used commonly to trigger Enhance Performance (Explosives X) with the Sigil of Battle to get 6-9 stacks of Might to empower the next attack. GW2Guru’s Grenadier build should explain it.
Channelled skills on associated kits -> Stow kit: You can channel Flamethrower’s #1 (although why anyone does that is beyond me), press the kit’s slot # again to stow the kit, then use other kits or weapon skills. You can also do the same to Elixir Gun’s Fumigate and Toolkit’s Gear shield and Magnet Pull. This is good to hide burst combos from other players in WvW and PvP, as well as queueing up your next burst skill in your rotation. Look up the “Bo-Bomber” build for a video explaining how to use this trick.
Animation cancelled movement skills: Jump Shot used to have awful aftercast which was remedied by swapping to another kit. You can still do it, but it’s less necessary now. Elixir Gun’s Acid Bomb leap can be cancelled mid flight by spamming “Drop bundle” when you want to land. The dodge at the end of Rocket Boots can be realigned in direction by flicking your camera to the desired direction of your roll before your flight completes.
