so what is engineer like is it as overpowered as you feared
MP is balanced, no one class is overpowered, like some classes in Mass Effect 2.
I know Sentinel class is a nerfed in the singleplayer, if you use tech armor it adds 80% to your cooldowns. Not sure if it is in MP.
The only class that comes close to overpowered in MP is the infiltrator. Basically you can cloak and do heavy attack to every enemy, early on. Once the mech, Phantoms, and nemesis show up you can no longer do that. Well you can try but it's going to do badly.
I love the engineer class in Mass Effect 3, It was so dam boring in ME2. I'll most likely be playing as a Adept, Vanguard & Engineer. I don't like how Adrenaline Rush works in ME3. It suppose to slow down everything around you. It doesn't do that anymore. It just increases your Weapon Damage for X amount of time.