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. ^^