First Insanity trilogy playthrough advice

1. Drone's chain lightning evolution at rank 6 is useful at zapping multiple enemies, but just do not be surprised if you find it underwhelming. If the enemy A.I. in ME3 was like the enemy A.I. in ME2 (always attack the nearest threat), then a drone and turret combo would be a whole lot of fun. But the enemy A.I. in ME3 chooses who to target based on a bunch of factors on what is considered the biggest threat, and some enemies will ignore your pets completely.

2. What is 'fun' is completely subjective. What you and I find fun -- or anyone else for that matter -- may be completely different. I find it can be fun, but moreso I just find it the most effective combination that the Engineer has at its disposal. I ran a full playthrough 'pets-only' build (combat drone, sentry turret, and defense drone) and it was effective, but I had to take some really gun shotguns to make it fun and effective.

3. Liara's Warp can detonate all types of explosions. Javik's Slam can detonate all types of explosions on unprotected enemies (enemies with no shields/barriers/armor). You could take a biotic bonus power such as Lash or Reave, although as I cautioned before, taking a detonating biotic bonus power on the Engineer will mean you will tend to avoid using any tech powers at all, making the Engineer kind of pointless. (Might as well be a Sentinel or Adept by that point).

Just a thought, maybe dump your A/P Ammo and just put a piercing mod on your SR... re-spec with a biotic bonus power that you can use to combo with Liara when you take her with you)... that way you can get in some tech combos with Kaidan and also get in some biotic ones with Liara.

I think you'll probably like the Indra better than the Viper.  I recommend putting an extended barrel or concentration mod on it (to up the damage) and a piercing mod to help it pierce through those guardian shields (if you do decide to dump your A/P ammo).

At level 60, you should have enough points to take everything to Level 6 except 1 skill (which will top out at Level 4) and you'll have 3 points you won't be able to use or you can have 2 skills top out at level 5 with 4 points left over.

ETA:  ... and since Red is too humble to link to his own video, here is his Drone Master Engineer in action:  , which might give you some ideas to help make your experiences using them situationally more fun.
 

Engineer's quite good for Insanity with your Overload and Incinerate. In ME2 everything around seems to like attacking your drone which allows you to get away quickly or pick them off.
TBH... I just pick armour that looks nice and the teammates I like Silly, but I've always managed. I'm quite shallow but enjoy the challenge.

Update: Did first Rannoch mission, did Samara's mission (love that one) and Jacob's. EDI seems pretty indespensiable as an Engineer, and that's ok cause I find her interesting. Kaidan, my LI, I wish was a little better. His Overload is good but seems like Garrus is better. I like using Tali and having two Combat Drones annoying people lol - and it's useful to stunlock some enemies.

Question: Haven't done Omega, Leviathan or Citadel. I always do Citadel right before the final push - but, do you guys do Omega/Leviathan right before Citadel? Wondering maybe from a lore perspective when it's best to do them.

P.S. Defense Matrix has been very useful as a bonus power. Getting shields back instantly AND that 25% damage bonus to tech powers is quite nice.

Depends. I typically do it after curing/sabotaging the cure, since Tali is not available for it anyway, and once Tali is on board I complete the Rannoch arc since it makes no sense story-wise for Shepard to ignore it and go off doing other missions.

Otherwise, if I want to save money on the mods, I wait until after the Ardat-Yakshi Monastery so I can get the full 10% store discount.

Update - finished all the DLC! Took all day yesterday to get through the end of Omega, Leviathan (really love the lore on that one) and Citadel. About to head to the Asari Councillor for the home stretch. Trying to finish so I can play Andromeda tonight.

One comment. MAN. Forgot how hard the beginning of Citadel is, especially on Insanity. As an engineer, I tried the first couple of sequences w/ stealth (after you crash down all the floors) and failed miserably. Had to high-tail it and just run through all the mobs. Had to do the same thing trying to get to the car lot. There's just too many mobs that flank you, and me stuck by myself with just that crappy gun. Felt impossibly. I did a mad dash and used a combat drone to stun-lock a few mobs. Took like 7 tries but then made it. Whew!