Being an engineer requires just as much focus over the battlefield as any other class does, this guide will provide with simple, but effective strategies to winning as an Engineer.
THIS IS PURELY FOR MASS EFFECT 3, I DO NOT KNOW IF THESE TACTICS IS WORKING IN ME1 OR ME2 SINCE I HAVE NOT PLAYED AS AN ENGINEER IN THOSE TWO GAMES
Being the Engineer:
As you may know, an Engineer has total control over all synthetic and robotic enemies and allies in the entire game. As an Engineer, your combat abilities with conventional weapons are not greatly diminished, but only so. You are unable to do whatever the Soldier class is able to do, such as throwing grenades, Combat Mastery, and special types of ammo. Your biotic abilities are also greatly diminished, but that does not stop the Engineer from ravaging the battlefield.
The abilities of the Engineer, is control over all synthetic and robotic allies and enemies. As an Engineer, you are able to turn synthetics and robots against their master (or THEIR allies). The most noticeable is Sabotage. Sabotage simple hacks the AI of the enemy, and puts it against it's allies. Sabotage can also be used as a way of stunning enemies, or overheating their weapons (if non-synthetic, that is). Another useful feature, that makes it easier for an Engineer to conquer it's enemies, is that he is able to lure them out, or force them, out of cover. The Engineer can utilize many of it's powers for this task, such as applying a Combat Drone at the enemies location, that stuns them out of cover. Or by using the deployable sentry turret, though, not as powerful or heavy as the Cerberus Sentries, this one still packs a punch, and can be upgraded to have missiles or a flamethrower.
These tactics allow your teammates to easily put the enemies down, by luring them away from cover. If you are to play an Engineer, you will want to focus on fast recharge time, and very heavy upgraded weaponry for easy take-down of the toughest enemies (such as the Banshee). If choosing an armor candidate for the Engineer, the Inferno Armor http://masseffect.wikia.com/wiki/Inferno_Armor would be a most adequate candidate. The Inferno Armor focuses on quick recharge time, and has:
+30% Power Recharge Speed +30% Power Damage
That was my guide, if you have any questions regarding the use of the Engineer, please write a mail to me at "firstname.lastname@example.org" thank you for reading, and I hope this guide helps you in playing The Engineer.