My main complaint with the beta, besides the lack of polish which simply comes with time, was the large amount of allies. I did get to kill a few enemies, but I was still largely bored. My advice would be to 'severely' cut down on the friendly AI to something like a small squad.
It'd be more interesting if you could make members of the squad be actual individuals with specific purposes. This way, if you plan it right you might be able to script events based upon these characters. That in my humble would drive the game along better than just watching them shoot at everything in sight (even the enemies they can't get to).
Either way this type of gameplay fairs better with a more isolated feel in my opinion. Most of the time you start off with a squad in a situation like the one you used, they'd all be dead almost upon arrival. The fact your squad is basically doing all the hard work for you, really steals away any tension. In fact the largest missing element was there wasn't any form of tension, and even if it's not Doom, you still originally based it off that, and building tension was one of its hallmarks.