ACR FLC COMPLIES WITH TCASII RA UNDER ZOB CTL. TA'S GIVEN; BUT NO CONFLICT RESOLUTION ISSUED.

Narrative

FLT FROM ROA TO PIT WAS ASSIGNED 7000 FT AND LEVEL NEAR PLEEZ INTXN ON THE NESTO 2 ARR. IT WAS XA30 AND ZOB CALLED TFC 10 O'CLOCK; 10 MI; 7300 FT UNVERIFIED. WE HAD NO INDICATION ON OUR TCASII AND THE SUN WAS SETTING DIRECTLY WHERE TFC HAD BEEN ISSUED. WE STATED 'NO CONTACT.' MOMENTS LATER; ATC CALLED TFC 11 O'CLOCK POS; 5 MI; 7300 FT. AT THAT POINT WE DID GET A TARGET IN BLUE ON OUR TCASII; BUT WE WERE UNABLE TO OBTAIN VISUAL CONTACT. THE TARGET TURNED AMBER; A TCASII ALERT WAS ISSUED. ATC CALLED TFC 1 MI 7300 FT. THEN THE TCASII GAVE AN RA 'MONITOR VERT SPD' COMMAND; FOLLOWED IMMEDIATELY BY ANOTHER RA 'DSND NOW!' I CLICKED OFF THE AUTOPLT AND FOLLOWED THE VERT NEEDLE DOWN 1700 FPM AND TOLD MY FO TO GET LOWER; TELL ATC WE ARE DSNDING. AT 6300 FT; I SAW A CESSNA 310; WHITE WITH RED TRIM; PASS OVERHEAD BY APPROX 800 FT. ATC TOLD US TO MAINTAIN 6000 FT AND WE SET 6000 FT. THE CLR OF CONFLICT COMMAND AND WE LEVELED AT 6000 FT WITH AUTOPLT BACK ON. THIS IS A SIT THAT COULD HAVE BEEN RESOLVED BY ATC ISSUING A TURN OR LOWER ALT TO AVOID A DANGEROUS SIT. IF WE HAD SEEM THE TARGET; WE WOULD HAVE BEEN TOLD TO MAINTAIN VISUAL SEPARATION. IS 300 FT ADEQUATE SEPARATION? HOW COULD I HAVE AVOIDED THIS ACFT WITH A HARD ALT OF 7000 FT? WHAT WAS CTR THINKING?