Its all about long range. Grab some type of sniping weapon, pop a steady, psycho, and a buffout. Stealthboys are nice, you can get that first crit. Before you fire, lay down mines in the path.
You can pick up a sniper rifle for free not too far from where you can get the Anti-Material Rifle in New Vegas if you spend a little time looking around. It's easily obtainable even at level 2 or 3 since it's simply on the ground. Load it up with AP rounds and you'll be blowing off Deathclaw heads left and right in a single shot. Even with standard rounds I've found it far more effective against armored targets than the Anti-Material or Gauss Rifles. Since it's not bolt action, you can empty the clip into a target pretty quickly. Beyond that, if you plan to use another type of rifle to snipe with, AP rounds or OverCharge packs become an absolute necessity against most targets.
I don't use VATS in FONV (I did in FO3, which made the Reservists Rifle my weapon of choice) and I've been finding a simple vanilla sniper rifle pretty effective with the new HP and AP rounds.