That's because some of the dev team are those people from Black Isle. 
I've tried the anti-materiel rifle but didnt like it. I'm sticking to my Gobi. BTW, you can get tonnes of 50mm from Hoover Dam.

I finally got that NCR Combat Armor. The only problem is that no one can repair the helmet. If you wanna repair it, you have to murder more Veteran Rangers to get another helmet (Incidentally, that's how I got the anti-materiel rifle too). Had to reload a previous save when I was at level 29 so that I can take Jury Rigging at level 30. 

Went to Vault 22. It was just too awesome. 

I never bring any of companions into Hoover Dam. They'll mysteriously 'disappear'. So I just tell them to wait outside.

Actually, I've been carrying around a dog's brain in my inventory but havent done the Rex quest yet. I killed this Fiend leader on one of the quests from Camp McCurran and one of her dogs had a brain in its inventory. I have ED-E as my non humanoid companion. It's like having R2D2. 

Not only that the power armors are quite useless, some of the perks as well. Grimm Reaper Sprint was my favorite perk in Fallout 3, in Vegas it only restores 20 AP upon successful kill. And IMHO energy weapons are dumbed down in Vegas. In F3, I just had that unique Plasma Rifle from the Rivet City quest and used it all through the DLCs. In Vegas, I'm not that keen on using energy weapons. Maybe it's because of the lack of Enclave soldiers.

For Rex there are a few brains that you can choose from - it will give him different stats increase.
- NCR = nothing
- Lady Gibson's = attack
- The Fort = health
- Violetta (Fiend) = speed

Have you tried looking for the unique weapons? The Q-35 Matter Modulator is pretty sweet.