MD80S ACFT BEING VECTORED FOR ILS APCH. FLC SAW ANOTHER ACFT WHICH WAS POTENTIAL CONFLICT WHEN APCH CTLR GAVE A HDG AND ALT CLRNC; APPARENTLY TO AVOID THE TFC. FLC RECEIVED A TCASII RA; BUT IGNORED IT DUE TO THE VISUAL ON THE TFC. RPTR CAPT BELIEVES THAT THE TCASII COMMANDS WOULD HAVE CAUSED A MIDAIR WITH THE SUBJECT TFC.

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WE WERE BEING VECTORED FOR AN ILS RWY 36L APPROX 20 MI SW OF DFW AT 5000 FT; 170 KTS ASSIGNED; FLAPS 11 DEGS. CTLR WAS VERY BUSY AND THERE WAS SIGNIFICANT FREQ CONGESTION. AT 5000 FT WE WERE IN THE CLR WITH A CLOUD DECK AT APPROX 4000 FT MSL UNDER US. I WAS THE CAPT AND I VISUALLY COULD SEE ANOTHER ACFT AT 11 O'CLOCK AND ABOUT 5-6 MI AT APPROX OUR ALT. CTLR; A FEW SECONDS LATER; INSTRUCTED US TO TURN TO 030 DEGS AND HUSTLE DOWN TO 4000 FT. THE FO WAS FLYING AND ALSO HAD ACFT IN SIGHT. AT ABOUT 4600 FT MSL; DSNDING TO 4000 FT; WE GOT A TCASII RA WHICH FIRST SAID CLB AND A FEW SECONDS LATER SAID CLB XING CLB. I TOLD THE FO TO CONTINUE THE DSCNT PER ATC. NO EVASIVE MANEUVERS WERE TAKEN. I ANNOUNCED ON FREQ 127.07 THAT WE HAD AN RA AND WE WERE DOING THE OPPOSITE OF THE COMMANDS IN FREQ CONGESTION. HAD WE CLBED PER THE TCASII THERE IS NO DOUBT IN MY MIND WE WOULD HAVE HIT THE OTHER ACFT. WE MISSED 500-600 FT VERTLY AND LESS THAN 1/2 MI HORIZLY. THE OTHER ACFT; A COMPANY MD80 AT 5000 FT SBOUND; DID NOT ALTER COURSE OR ALT. AT 4000 FT WE WERE IN AND OUT OF THE TOPS OF THE CLOUDS. CONTINUED TO AN UNEVENTFUL LNDG.