I started out by going for Cloak and Passive, fairly evenly, but I was having a bit of a hard time, so I respecced into Incineration Blast (the AOE version), Area Energy Drain, and then passive and I'm working on Cloak. I've got Disruptor ammo at lvl 2 at the moment.
So far, this set-up is working MUCH better for me, personally, on insanity. I have the sniper rifle, I have the cloak, but I tend to play the infiltrator a bit more like a caster class, at least in the early stages of a fight. Once the enemies are thinned down a bit, I can use the sniper rifle to drop a few more, then cloak, advance with SMG to finish them off. It's a personal preference for playstyle. I get the satisfaction of a good solid advance, playing aggressively, while not having to tear my hair out because I got too aggressive. Fits me to a T.
I enjoyed the Sentinel and Adept playthrus I had, but I didn't like how conservative you had to play (never got the hang of an Assault Sentinel, just didn't work for me, for some reason). The infiltrator lets me be conservative when I want to be, but then when the time is right, switch on the bloodlust and go bust a cap in a merc's @ss at point blank range.
Works for me, certainly won't fit everyone's playstyle, but give it a try if you like. It may work for ya.