DFC when you say
the task of ensuring that we do not collide with other aircraft is delagated to ATC
and
In VMC, then the pilot is fully responsible for avoiding collisions despite what ATC may be doing
I think it is better to say that ATC will assist the pilot in collision avoidance... IIRC the pilot is always, ultimately responsible for the prevention of collisions irrespective of airspace and IFC (hence ACAS procedures?)
(This debate on responsibility might be a good topic to prune off onto a thread of it's own?)