sucks to hear man

I'm finding Insanity to be pretty easy as an Infiltrator... maybe you should re-start as that class?
My team is Grunt and Kasumi. I maxed assassination cloak (+75% damage while cloaked), so on the Collector Ship I could go into cloak mode, and take out Collector Drones with one headshot even if they have full barrier! Grunt is a great damage sponge so he can draw the enemies attention while you hang back and pick off the bad guys with your rifle. You have the DLC? Kasumi's shadow strike skill is great at hitting for big damage from a distanse too. Grunt's concussive shot is good at crowd control as it knocks dudes down at higher levels. The SMG you get on Kasumi's mission is amazing as an Infiltrator too, extremely accurate even at a distance.
I'm also doing every sidequest I can straight away, and constantly checking stores for upgardes, which is helping alot.
Also I can't count the number of times where the cloak has saved my ass. If youre jumped by some enemies and you're about to eat it, as soon as you activate your cloak the enemies forget you're there! It effectively makes you invincible, and you can run back and find some cover.