Generally speaking (I'll post my build later, but I'm at work), my engineer is built for mobility and conditions. That means pistol (bleeding, poison, confusion AOE) and elixir gun (bleeding, poison AOE) for weapons. I also include Elixir R (refill endurance) and rocket boots. I've been using the medkit mostly for its toolbelt heal (quite a large heal with a shortish cooldown), but have been tossing between that and the healing turret. I don't remember all my traits (again, at work), but one of the most critical for me is incendiary ammunition (crits inflict burning).
Equipment for me is rabid stats (Condition Damage, Precision, Toughness). I've been slowly aquiring Nightmare Runes, but that'll be a slow process that requires additional Twilight Arbor runs. I'm also doing torment on a crit. I think it's one of my weapon sigils, but I cannot recall off-hand.
What I end up with is a build that allows me to do a ton of conditions and critical hits, while being extremely mobile (four dodges, two abilities to simply be on the other side of the field; one which works while immobilized). I also have a good amount of ability to throw down heals. (obv if I switch to healing turret, but also elixir gun tool belt skill, and its #5 ability). This includes the toolbelt skill for Elixir R, which lets me revive downed allies (not as effectively as warriors and guardians).
The bad parts of the build - I'm very fragile. Ironically I'm even more fragile against conditions (since I don't have any vitality equipment), even more so against conditions that do damage to moving targets. In PvE that means staying ranged as much as possible; melee against a champion is a sure way to die. This may invalidate this build for you, given your latency concerns; you have to be able to dodge through red circles. I'm not super-skilled at WvW, but for me this build seems to require edging around a big fight. I try to keep an idea of how the battle is flowing so I don't get cut off; but it's really, really easy to find yourself down before you know it. In short, this may not be the most viable WvW build, but I have a lot of fun being a force monkey. :P
Hope that helps.
(Edit: I also use a shield. It lets me push away opponents, and also acts as a blast finisher.)
» Edited on: 2015-02-18 08:41:16