Infiltration relies on maneuverability and heat shots. But mostly remembering where the infinite spawns are...
While playing on insanity as an Infiltrator. My usual strategy consists of sitting back and sniping off the enemy from a position of superiority. Only when I am on my last thermal clip do I realize that this is one of many infinite spawns. And until I advance to a certain spot, the enemy will continue to line up until I am out of ammo and I will ultimately lose.
At this point I have a few options. Since I only have one clip of ammo left for my sniper rifle, and all the thermal clips dropped by the enemies are behind their lines thanks to my precise shooting. I have to switch weapons and advance.
I enjoy using Grunt and Kasumi on my team. (You'd forget all about the Human who cloaked if you saw an angry Krogan charging at you too.) I advance Grunt, cloak, then advance myself. During this dire situation as my thermal clip count continues to diminish; Kasumi is bombarding the enemies with her abilities. The instant kill from her Shadow Strike and the shock from her Concussion Grenades weed out enough of the opposition so I can safely advance.
After much panic, the rest of my thermal clips, and every ability on cool down. I have advanced far enough to turn off the infinite spawn.