Riverrock:
Well this is what flying quadrantal levels and such is for, plus a massive load of big-sky theory since you're putting your faith in the controller seeing traffic. In addition, if you were under a deconfliction service and the controller didn't register some traffic you'd still fly into it anyway because you wouldn't have been vectored away from it...?
However I would suggest that if the airspace was as congested as it would need to be in order to have a controller not pass all relevant traffic through workload or cognitive failure then a Traffic Service probably wouldn't be appropriate though I can't think of many situations where that would happen OCAS because I think nearly every approach/ radar/ LARS controller I've spoken to in that scenario has been spot on
