Might be a dumb question, but I'm curious about how you're speccing your GI, and what strategies you're using when you're in the the thick of it. I've never played Infiltrator seriously, just wondering because it sounds like fun.
I usually go 6/6/6/6/0
For Cloak, I use Damage, Recharge Speed and Bonus Power
For Proximity Mine, I use Radius, Damage Taken(Increase damage from all sources by 20% for 8 secs, very important!) and Damage
For Hunter Mode, I use Power Recharge, Power Damage and Damage
For Networked AI, I use Weapon Damage, Power Damage and Weapon Damage.
Some people might have different builds, but i like this one. Pure damage spec and better radius for the mine so that the Damage Taken skill affect more enemies.
I equip my Claymore with the mods for more damage(or more armor penetration like DY_nasty said) and more accuracy(Seriously, i can kill almost anything at long range, unless its very far)
Basically... i use Cloak, point in the middle of a group and throw my Proximity Mine and once it explode(you wont lose your cloak after using 1 mine) i proceed to aim and shoot at the most annoying guy of the bunch (like Ravagers, they die after ONE mine and ONE Claymore IV shot on Silver). Then i run and hide until the cooldown of Cloak is gone. If you throw another mine on the first group you attacked, you might kill all of the weaker enemies left. Repeat until everything is dead.