But I think the intent of the so called "DIR" system is to create a simple system that can be used in any environment for any type of diving. It's my personal opinion that for tech dives the gear config and the team approach are just what is needed. And yes, even in shallow openwater diving in perfect conditions, the system works great. My contention is that I don't think the shallow openwater diver will "die" sooner if he wears a more traditional set up.
BTW, why isn't a dual-isolation manifold with primary reg and back up reg on the other post a 'reliable independant air supply'?