http://gw2skills.net/editor/en/?fcAQFAUlspiYX3SfF17IyoCdmoHV2jRZfeQfpFEC
Grenadier/Elixir Gun Build.
30 Explosives, for Grenadier and Short Fuse. Explosives 10 trait is your choice.
30 Alchemy for Self-Regulating defense, Fast Acting Elixirs*, Cleaning Formula 409*
*these two skills became partially bugged in the most recent patch.
10 in Tools for speedy kits.
Due to current bugs (see* above), it may be better to go 20/20 alchemy/tools and pick up static discharge and inertial converter. Likewise, the healing skill is dealers choice. Decent arguments can be made for elixir H and med kit.
Gear is also dealers choice. Power/Crit gear will synergize well with rifle and grenades; with elixir gun, alchemy traits, and elixir s providing reasonable survivability (more on that later). Vit,Toughness, or Condition Damage gear will enhance survivability while still providing decent damage by way of conditions from both Elixir Gun and Grenade Kit.
Tactics
Standard grenadier tactics apply for usual WvW, Spvp point scenarios. Grenades are one of the few engineer kits that are undisputedly good, as they are one of the best ranged AoE’s in the game. Likewise, I won’t go into Rifle+Grenade tactics.
I’m going to describe how to use elixir gun in depth because, honestly, there isn’t too much on these forums about how to use it. There’s about 1 or 2 good videos and that’s it.
Tranquilizer Dart
Elixir gun use is what gives you an edge. Elixir gun 1 applies a decent bleed, and weakness. Weakness reduces damage inflicted by target 50% of the time by 50% aka “Glancing blows.” What this means is against most Warriors,Rangers, Thieves, Guardians, Engineers, you reduce their overall damage done by 25% (roughly). This is huge, especially in 1v1’s since you can keep weakness up 100% of the time.
Super Elixir
The next most useful ability is Super Elixer, which gives AoE regen and creates a Light field. http://wiki.guildwars2.com/wiki/Light_Field
It removes a single condition to you and all nearby allies when initially applied. If no conditions are removed, it applies retribution. More importantly, for each projectile attack that goes through it (the attack itself does not have to hit), it has a 20% chance to remove a condition. This is very nice seeing as Pistol 1, Rifle1, and Elixir gun 1 are projectile finishers. This is very useful (for you and your team) against condition heavy teams or builds, particularly those that rely on mesmers (confusion), necros, rangers, and engineers.
Acid Bomb
The third most useful ability is Acid bomb, which is an excellent mobility skill. It’s Rocket Boots without the self knockdown, without the stunbreak or immobilize break, and with fewer bugs. It’s an excellent mobility skill, plain and simple.
Elixir F
Next most useful is Elixir F. Elixir F is a cripple. Unlike net shot (similar rifle skill, immobilizes instead of cripples) it actually hits much more often, for whatever reason. Moreover, it gives nearby allies and yourself swiftness. Very useful for preventing escapes in both sPvP and WvW as it slows down enemies AND speeds up allies.
Fumigate
Finally, we have fumigate. AoE condition removal for our allies (sweet), and decent damage to boot. Very similar to flamethrower 1, except it actually hits more often than it misses.