The Engineer is a class of many roles, and it can be hard to figure out how best to play a class that has so many gadgets at its disposal. Vox tries to narrow down the roles, focusing first on general engineer strategies, then discussing strategies for each of the masteries in turn.
As an engineer, your playstyle will be deciced mostly by your choice of mastery, but there are some things that are universal no matter what you play. Your turret is a significant portion of your DPS, so whenever possible, have it out. This works well when defending points, trying to hold a flag, or locking down a chokepoint, like the area near the artifact in Mourkain Temple. Favor the turret that your mastery benefits, but use what is best for the situation. Use your tactical abilities wisely - use barbed wire to slow down runners, or save your own, or stop a flag rush. Use Point Blank to remove dangerous enemies from the situation or buy your healers breathing room. Always have Flak Jacket on, unless you are too pressed for time to use it. And no matter which mastery you play, target enemies in this order: Healers, RDPS, MDPS, Tanks.
The path of the grenadier is arguably the engineer's most powerful mastery. The combination of high damage AoE DoTs and a cheap, efficient AoE debuff means that you can rack up huge numbers. Throw frag grenade, acid bomb and sticky bomb on large groups of enemies and watch the damage tick. Use flash bomb to shut down healers and casters and fire bomb to finish them off. You will have to play up close to make the best use of your grenades, so make sure you know how to use addling shot, barbed wire and point blank to the best of your ability. Pick up the throwing arm tactic to give yourself a ranged edge and the extra powder tactic to increase your DPS. A good strategy with grenadier is to sneak around to the back so you can lay the hurt on destruction's weaker healers and ranged DPS. Napalm is one of your best abilities - use it in chokepoint and watch your enemies suffer. It is also extremely useful in castle sieges. If you throw it onto the ram and combine it with the oil siege engine, you can lay waste to the besieging army with ease.