I've been spending a little more time playing as the original (non-Cerb, non-N7) human classes lately, and I'm beginning to detect a pattern: the original human classes, with the possible exception of the Infiltrator, are all geared toward maximizing power recharge time and spamming the you-know-what out of one or two seemingly unimpressive (but not really) abilities. With the Adept it's Shockwave. With the Soldier it's Concussive Shot. With the Vanguard it's the infamous Charge/Nova combo.
With the Human Engineer it's everything. Like Spamfest '98.
Combat Drone can be spammed. Incinerate can be spammed. Overload was flat-out MEANT to be spammed. If there was ever a class where it's possible to top the scoreboard without ONCE pulling the trigger, it's the Engineer.
With that in mind, it should be pretty easy to see where I'm going with this build...
1. Combat Drone. Back when I did my Mass Effect 2 Power Rankings, I rated Combat Drone as the overall best power in that game. I have yet to put together such a list for ME3's multiplayer (or single player), but it's a safe bet that this will be near the top yet again. The multiplayer version has lost a little bit of its original appeal (Combat Drone no longer draws the undivided attention of EVERY enemy in the area), but make no mistake, it's still a terrific power.
What makes the Combat Drone so effective is that it's still the best way to project your firepower without presenting yourself as a target to the enemy. It's completely expendable, yet can kill minions with an efficiency rivaling that of many Bronze-level human players. Add the new rocket attack, and it becomes an effective measure against big armored stuff, as well. You'd be silly NOT to level this thing to rank six.
Your choice at rank four really depends on whether you plan on taking the rocket option at rank six. If you are (and you should), expanding the Drone's overall damage and longevity should be your focus here. I was always partial to the explosion effect in ME2, but that was for the pre-rocket Combat Drone.
At rank five, even more damage and shield protection is probably the better choice. I DO like the stun effect though, so it's definitely worth a look if you already went with damage/shields at rank four.
The rockets should be an easy selection at rank six. The pulse stun chain is probably sweet-looking against huge crowds of low-level bad guys; but there are plenty of other ways to deal with THOSE. Arming your Drone with rockets gives you another legitimate option against bosses....and it's still pretty good vs. little stuff, too.
2. Incinerate. The more I use Incinerate, the more I like it. With the proper bonuses applied, this power's progressive damage works wonders against pretty much everything not wearing a shield or barrier. Whether you're softening up light enemies for a quicker kill or spamming the power repeatedly to wear down the armor of bigger foes, Incinerate will likely be your Human Engineer's workhorse power. If you're debating whether to level Incinerate or Overload to rank six, choose Incinerate. Armor is generally much more of a pain that a shield or barrier.
At rank four, I like the 30% damage bonus for this build. Radius DOES make it less likely the enemy will dodge your fireball, but since I typically gear this power to be most effective against the really big stuff (which never dodges anything ever), I don't much care about that.
At rank five, recharge is undeniably nice, but an extra 50% damage over eight seconds is nicer. This power can be spammed either way, and the progressive damage lends itself to longer waits between casting.
At rank six, you can finish making this power your dedicated boss-killer by taking the 50% bonus against armored enemies. Incinerate is already great against armor; this evolution makes it even better.
3. Overload. Overload....busting fools' shields since November 2007. And while shield-killing is certainly Overload's primary purpose, it can also be used to effectively stun any non-boss-type to set up for an easier headshot.
I like Overload, and use it quite a bit. However, I find that since it's great for taking down shields at pretty much any level, it's usually best to stop putting points into this power at rank four. This lets you pick either a flat 30% damage upgrade or the chain-lightning thing.
I like the chain-lightning thing; as its effect is noticeable almost immediately- letting you stun TWO enemies instead of just the one you targeted.
4. Alliance Training. Alliance Training is the Human Engineer's first passive power; granting percent bonuses to weight capacity, power damage/force, and weapon damage. Since this build is centered around heavy use of all three of the Human Engineer's castable powers, leveling Alliance Training to at least rank five is practically a must. Pick the bonus to power damage and force at both rank four and five.
You could probably sacrifice the points from rank six if you wanted to level up Overload some more, but I'm personally partial to the 10% bonus to weapon damage at that last evolution.
5. Fitness. Fitness is this class' health/shields/melee passive power. Melee is a non-factor for this build, so points at any of the advanced levels should be used solely to boost health and/or shields. I've never had a survivability issue with this class, so I generally just level Fitness to rank four early on and just leave it. That gives me 700 health and 700 shields. Not bad. And not much less than the 850 that I'd have if I'd invested the points for rank six. For this build I just don't think it's worth it.
Combat Drone to rank six, damage/stunner/rockets
Incinerate to rank six, damage/progressive damage/bonus against armor
Overload to rank four, chain lightning
Alliance Training to rank six, power damage/power damage/weapon damage
Fitness to rank four, health and shields
Recommended Weapons: Naturally you'll want to go with something lighter here...perhaps your favorite SMG or pistol, or the Avenger. I'd say just make sure your recharge bonus ends up no less than 170%. My personal favorite for this build is the Arc pistol. It has ammo issues, but packs a decent punch, is fast, and just kind of fits with the class.
Recommended Gear: Since I like the Arc Pistol for this build, I'm partial to the Pistol Amp (or whatever it's called) that grants a percent bonus to pistol damage. A power damage bonus would be okay, as well.