Which bonus power would be best for an engineer class on an insanity play-through or is it better to take a different class and if so what class/Bonus power should i take? And does anybody have any advice on the best way to approach an Insanity play-through? And what things would make it easier to do? Any advice would be greatly appreciated
Lets take a look at each bonus power and break it down individually:
Ashley (assuming she's alive):
Kaiden (only if he survives virmire):
Javik: I don't have him so I'm leaving him out.
In conclusion here are the good ones to consider:
Reave/Energy Drain for survivability
I fully disagree with Marshal Shepard's assessment or the engineer being too squishy for insanity. My favorite class is the engineer and I have completed ME2 multiple times on insanity and ME3 once on insanity.
First, the ability to double your squad size with a combat drone and a sentry turret within the first 6 seconds of an engagement is unmatched. Because the Mass Effect AI forces the enemy to deal with drones first both of those abilities enable you to get inside the enemies decision making cycle and thus influence the battlefield on a major scale. So while your squadmates are taking advantage of the chaos the engineer just created, the engineer can either assist with target engagements or continue to influence the fight through continual spamming.
Second, incinerate is one of the most powerful and effective powers available. Not only does it deal massive damage, but it damages every level of protection, including regeneration. Add to this the "panic" effect and once again the engineer influences the fight by interruption the actions of the enemy.
Third, overload is now more powerful than ever in Mass Effect 3 since warp has been changed to no longer strips barriers, and overload has been changed to strip not only shields, but also barriers. Now, not only does overload strip valuable protection, but it stuns opponents and overheats weapons. With these changes to overload in ME3 energy drain is somewhat superfluous. The engineer now must decide if they would rather have the weapon overheat effect of overload, or the draining effect of energy drain.
Fourth, cryo blast although not damaging allows the engineer to remove enemy numbers from the fight by snap freezing them. In the sequence of a battle by the time the drone and turret have been on the field long enough to strip shields and barriers the engineer can begin freezing opponents thus providing easy targets for the squad.
Fifth, sabotage is the only power available that will turn the enemy against itself. Assuming control of a turret, Geth Prime, cannibal or marauders is an extremely effective way of reducing the enemy force while conserving your own. If done properly, the engineer can add 3 members to the squad; a combat drone, a sentry turret, and a sabotaged enemy.
Sixth, because Mass Effect does not differentiate specific armor types by class, the engineer is able to wear the same level of armor as a soldier. Add to this the ability to modify armor and select bonus powers and upgrades and an engineer's health and shields will surpass and can rival any member of the squad.
Finally, once again because Mass Effect 3 no longer differentiates specific weapon types to specific classes, the engineer is able to carry a high damage assault rifle such as the Mattock or high capacity sniper rifle such as the Raptor. Thus the engineer is able to engage and destroy targets at any range and at any point in the combat sequence.
When compared to the most common player strategies of cloak-shoot-repeat, charge-shoot-repeat both which force the player to target a single enemy at a time, the engineer's strategy of drone-turret-overload/incinerate allows the engineer to target 3 opponents within 6 seconds, tying two of those opponents up for prolonged periods.
This analysis, I believe demonstrates not how squishy the engineer is, but rather how powerful and useful the engineer actually can be even on insanity level.
The best way to tackle Insanity is with a character that's close to level 60 (2nd playthrough after importing from ME2 or 3rd playthrough without importing). Weapons and tactics requiring you to be exposed for long periods of time will be less effective, so a class that relies heavily on powers and high-damage weapons (Sniper rifles, shotguns, heavy pistols) is preferable. Biotic detonations are quite effective, taking Liara and Javik (From Ashes) will let you do a detonation every 3 seconds or so, which is quite nice.
Positioning your squadmates can help quite a bit too, as they will be less likely to charge a bunch of enemies with automatic weapons that way. Speccing a squad member to be a tank (High health, high shields, barriers, forticiation, etc) can also be helpful.
The choice of a bonus power largely depends on how you're going to play. If you wish to go in guns blazing, Barrier, Fortification and Defense Matrix will be useful. If you wish to rely on powers instead, something that fills in a gap in your arsenal is preferred (Such as Energy Drain for Infiltrators, who lack an ability that targets shields).
the problem with playing Engineer is that you're too squishy for insanity. I'd suggest you made an infiltrator because it has cloaking ability that can get you out trouble, cryo ammo that disable your enemies, incinerate for armored foes, and high dmg with sniper (you can use M-99 saber or chakram launcher if you desire, they both have high dmg and weight less than sniper rifle). Don't bring too many guns, you need the cd reduction. The only thing that lacks on an Infiltrator is ability to remove the enemies' shield/barrier, so i'd suggest you take Energy Drain for your extra ability so you can sustain and deal dmg at the same time. I'd take Liara for disables and the 3rd squadmate is really up to you. With that set-up, I was able to go through insanity mode w/o any real problems, even against kai leng. (energy drain is too nice to pass up on)
I would go for an ammo power, I know the Engineer is a powers class it's still nice to have damage bonus and backup fire during cooldowns! A defense drone would also be good because you could get an extra 4 allies on the field:
Defense Matrix is a good option. It can increase tech powers damage and helps to survive in complicated situations. Engineer do not need additional active powers, he already has the strongest combos. Sabotage(+100% damage from tech powers)->Cryo Blast (optional)->Incinerate(if frozen +100% damage+electric combo after Sabotage)->Overload(fire explosion, if chain overload can be multiple explosions). Cerberus troop just can't survive in this hell. Almost the same we can achieve with Infiltrator + great damage of sniper rife. He only can't make fire explosion (Energy Drain can do it only of enemy has shields), need help of squadmates to finish combo.