Sorry about taking so long to get back to you. I'm stuck on trying to get Grunt and was stupid enough to bring the two bring Garrus and (I'm blanking on the other name but the human mercenary). I can't figure a way but do you know if there is a chance I can go back to the Normandy 2 to replace my partners? Thank you.
Regarding Insanity mode on Mass Effect 2, I beat it with an Infiltrator. You don't need to buy any equipment packs. The weapons specialisation that you get on board the Collector vessel gave me an absolutely awesomely upgraded Sniper Rifle, and the Locust SMG from Kasumi's DLC is the only other weapon I used, as it covered short-ish to medium range, and beyond that, the Sniper Rifle was the way to go.
I wish you the best of luck with your Insanity playthrough, and I'd be interested to hear how it's going. ^^