I'd agree, except that I can see it developing into an endless game of ping pong: ISP says contact OR, OR says "not us, contact your ISP". How do we know whose responsibility it is? That's why there was one point of contact in the first place.
I have a problem at the moment (a DLM reset) where it'd be sensible, and easiest, to talk to OR. Any chance? No. Everyone would be at it, "just in case". They will always be under pressure to cut costs, which means more automation and less scope for changing anything. We have to live with the consequences. Mistakes when they happen, which they will, will be big ones.
The only way I think it'd work is if everyone had to take a line contract from OR, separate to their broadband contract (except with FTTP, mobile and Cable). Then it would only work for traditional line faults, like it used to when we had voice-only telecoms. We can't turn the clock back, however hard we try.