Comments - HankJJ

I assume you were playing HL2 Entanglement where Alyx is scripted to rush the room filled with soldiers. Yeah, it's always has been a problem even in vanilla HL2 that you had to babysit Alyx and Barney since they rely entirely on the script.
Combine soldiers output the same amount of damage as the Player on diabolical difficulty, combined with their ability to use the shotgun double-barrel mode gives them enough firepower to rip you into shreds should you let them get close to you. That's why they were capable of taking out strong targets such as Antlion Guard (especially if it got hit by an energy orb from Nova Prospekt soldier).
The Elites are meant to be the deadliest overwatch ground forces since their elites, so for them to have their energy orbs deal only 15 like in vanilla where it can't even kill a headcrab while the Player's can disintegrate almost every NPC is illogical considering also they're the same orbs. Therefore they now have almost the same status as the Player (much like the Replica Elites from FEAR on extreme difficulty).

Here are some tips:
1) If you ever found yourself surrounded by groups of enemies on the diabolical difficulty, use your rockets or spam alt-fire. You won't stand a chance for a fair fight.
2) Don't engage hard enemies such as NP or Elite soldiers with weak weapons such as SMG1, because it won't make them flinch.
3) If you're fighting Elite or NP AR2 soldiers, make sure their line of fire isn't directly clear from props or corners since they won't use their alt-fire unless they got a clear viscon.