Yelena was operating alone, no companions, and was using her preferred loadout; Laser Rifle, Gauss Rifle, Laser Pistol and Shocksword, and decked out in Lyon's Pride power armor and a composite recon hood. Totally outgunned and out-armored, I had to cleverly use cover, snap off a few shots, and move before the incinerators flanked me. I have come to really, really hate Hellfire troopers. Though Sigma Squad was a total walkover. The fight for Adams AFB and the thrash through the mobile base was a grinding hell the likes of which I haven't played in a long time. Gods, seeing that orbital alpha strike was so satisfying.
Now it's time to start working with the Brotherhood full time, clearing out the DC area and building something new from the rubble.
Why was Yelena using Lyon's T45d when T51b and Hellfire was available? Because she's a Brotherhood Knight, dammit. She earned that armor. The other two are simply spoils of war.