So I decided to bring my ME2 Engineer import over to Insanity, (This being my first Insanity run thus far.) I must say, this run is very challenging yet very rewarding. I spent roughly two hours or so doing the Grunt mission, using each attempt to help pinpoint the perfect cover for me and my Squad. So far I have been bringing Miranda and Garrus with me and they have been playing exceptionally well. The boss fight in the mission was slightly challenging but once I was able to find the proper cover, ended up becoming easy. Use the drone to disable each Korgan until their armor's stripped, then cryo + burst. Once the Krogans were destoryed, I positioned myself behind the crate, preventing the mech from flanking me only to wear it down with overload. Once they were done, the boss was fairly easy.
So far I think this class plays exceptionally well on Insanity, yet is completely underrated. You have to rely on positioning, squad combinations and strategies in order to succeed, whereas the Soldier and Infiltrator have slightly more leeway.
Does anyone care to share their Engineer experiences?