Regarding traffic advisories, of course a traffic call would be in order if in my judgement the info I had placed the aircraft in unsafe proximity or they may get there. Honestly personally I probably call too much traffic, but I don't care I like for pilots to keep their heads on a swivel, if I got nothing better to do, I call traffic. In a terminal environment you only need to communicate with one aircraft for visual separation. The use of "maintain visual separation" in such a case would largely be me (if I was the controller) saying to the tapes(in layman's terms "talking to the tapes" =C.Y.A.) "Hey do what you need to do, but do not to hit that aircraft" even though as the PIC you are already authorized to do that whether I give you permission or not. In your scenario there is no separation standard between VFR and IFR in Class E airspace so "Visual separation" is an unnecessary step. However to me if I conclude the situation warrants it (you can usually tell which pilots you should talk to the tapes for within one or two transmissions) because I am not completely sure that the pilot knows that I am not separating him from that other guy, I'll tell them to maintain visual sep.
Visual Separation
