What is most important to remember about the engineer is that - based on what you’ve chosen as your mastery - you will play the class radicaly differently. A rifleman will stand farther back, but have less AoE and overall damage, a grenadier will do the most damage, but has to get closer to the action, and a tinkerer has tons of gadgets, but relies on a single ability and has less overall damage than the other two masteries. Find which one you like, or play and adjust your mastery selection to the one you most identify with.
RvR Abilities: Rifleman
Your baseline ability is going to be a little different depending on what you chose as your mastery. This is because following a mastery path improves the damage and efficiency of the abilities in that mastery. If you chose Rifleman, you will want to use Gun Blast for your bread and butter. Since you’ll need to stand farther back to be effective, this will effect the other abilities you use. Make sure that you’re frequently using Incendiary Rounds and Hip Shot to do high amounts of single target damage, and make good use of Crack Shot to increase your survivability, and Snipe to take down runnners. Don’t overuse this last ability though, as it has a long build-up period.
You can use Phosphorus Shells if you find them useful, but it is a short range AoE, and doesn’t fit that well with the rest of your abilities. It’s up to you if you think it is worthwhile. Definitely pick up Hollow Points, and use Signal Flare as often as you can, as it debuffs your target’s defenses. Perhaps your most important rifleman ability is Focused Fire. As soon as you pick this up, replace Gun Blast on your hotbar and never look back - Focused Fire takes rifleman from a decent mastery to an awesome one.
RvR Abilities: Grenadier
Unlike when playing as a Rifleman, when playing a Grenadier, your bread and butter ability will be Firebomb, not Gun Blast. Also, you will want to make significantly more use of Acid Bomb, as it does damage and debuffs your enemies to your main damage type, corporeal. Try and mix Fragmentation Grenade and Sticky Bomb in with Acid Bomb when attacking large groups for huge amounts of damage. This is especially useful in RvR scenarios with chokepoints, like Mourkain Temple. Also, once you get it, make good use of Napalm Grenade, especially when defending keeps. Strafing run is useful, but not essential, and Flash Bang and Concussion Grenade are situational - use them sparingly, and only when needed. You get most of your useful abilities earlier than Rifleman and Tinkerer, so take advantage of that and get used to using them.
RvR Abilities: The Tinkerer
As a tinkerer, your options are somewhat different. You can adopt the playstyle of the Rifleman or the Grenadier (or a mix of both) but you don’t really have enough Tinkerer-only abilities until late in the game to play with them alone. Do make good use of Land Mine - it’s not very useful unless you have points in Tinkerer, and make sure you always have a turret up. It’s most useful when you are playing as Tinkerer.
Bugman’s Best is worth picking up - it’s only useful sometimes, but it is better to have it than not. Also, do get Lightning Rod even if it doesn’t seem like it does much damage. Paired with other tinkerer abilities and Acid Bomb, it can be an effective deterrent. Your most important ability as a Tinkerer is Electromagnet. This, combined with your AoEs and especially those of Bright Wizards, will allow you to lay waste to opposing armies of destruction.
RvR Abilities: Tactics
By the time you reach 40, you will have a great deal of breathing room when it comes to picking tactics, but it is still useful to identify which ones are worthwhile and which ones should be skipped. Almost unequivocally, unless you need the slot for something, you should take and slot the first tactic in your mastery, and all builds may want to consider Well Oiled Machine, as an instant turret is incredibly useful in RvR. Beyond that, your mastery tactics will generally take precedence over generic engineer tactics, with some exceptions. Steady Aim should find a place in your build, as the damage boost is always worthwhile. Tangling Wire is extremely useful in RvR, and should be taken unless something else takes precedence. Proximity Alarm can allow you to take out Witch Elves with ease, and may be useful if the are a problem for you. For Grenadiers, Expert Skirmisher can be a huge damage boost, but you need to stay conscious of your range. As always, mix and match your tactics to fit your playstyle, more than anything.
RvR Abilities: Morale
Morale abilities are somewhat easier to choose, as there are fewer of them, but there are clear choices for what you should choose for your morales in RvR. The first Morale you get, at level eight, Point Blank, will continue to be one of your most useful for the rest of your career. The massive knockack is one of the best defenses you have against melee careers. Unshakeable Focus, your first rank 2 morale, will remain incredibly powerful until 40 and beyond. For rank 3, Explosive Shots is acceptable, but Cannon Smash is probably far better for RvR. Finally, if you choose to take the rank 4 morale for your mastery, use that, otherwise, Hail of Doom is perfectly acceptable.
The engineer gets a veritable truckload of abilities, and even if they could all fit on your action bar, you would never be able to use all of them effectively all of the time, so it is important to lock down a smaller segment for your specific use. As always, what you use depends entirely on you, but hopefully this guide will help push you toward deciding your own set of tactical and effective abilities.
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