I think the final report is going to say that Army pilots likely routinely busted altitude restrictions and the presence of helicopters on that flight path caused repeated RA/CA warnings. The warnings were likely so prevalent that controllers ignored them.

Lines of fault:
1. Allowing VFR helo flights along the Potomac that cross active runway glide paths
2. Repeated altitude restriction violations by Army pilots, causing multiple CA's
3. A sense of "accepted danger" by controllers, who placed too much trust in the Army pilots and didn't control their airspace tightly enough

Obvious step here is to ban those flights up the Potomac -or- at the very least make Army Aviation file an instrument flight plan. That way they don't get to freelance anymore and have to instructions from Reagan and the Potomac TRACON. A busted altitude ceiling then would generate 'Possible pilot deviations' and phone calls from the FAA to the Army.