A DELAYED DSCNT SPONSORED BY A TASK SATURATED ZFW CTLR TRIGGERS A POTENTIAL CONFLICT BTWN 2 MD80 ACFT WITH LATE PREVENTIVE ACTION FROM D10 APCH CTLR.

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AFTER HOLDING FOR OVER 1 HR; WE WERE ABOUT 4TH OR 5TH ON THE UKW8 ARR INTO DFW. THE CTR (JUST BEFORE HANDING OFF TO APCH CTL) CTLR WAS VERY TASK SATURATED. ONE OF THE MISTAKES I DISTINCTLY REMEMBER CTLR MAKING WAS CLRING US DIRECT TO A FIX THAT WE HAD JUST PASSED. CTLR KEPT US HIGH ON THE ARR TO THE POINT THE CAPT ASKED FOR A DSCNT TO MAKE THE ALT RESTR. WE WERE HOLDING AT; AND STARTED THE ARR AT; FL240. CTLR STEPPED US DOWN A COUPLE OF TIMES TO ABOUT FL190 AND GAVE US A VECTOR TO GET SOMEONE IN AHEAD OF US. CTLR FINALLY CLRED US DIRECT TO BAMBE; THEN TOLD US TO PASS KAGLE AT 11000 FT AND 250 KTS. THE ALT RESTR WAS GOING TO BE CLOSE EVEN WITH FULL SPD BRAKES (WE WERE ALSO LIMITED TO 280 KTS IN THE DSCNT). WHEN HANDED OFF TO APCH CTL; THE CAPT CHKED IN WITH THE ALT WE WERE CLRED TO (11000 FT); AND THE APCH CTLR SAID NOTHING OF A POTENTIAL CONFLICT. WE WERE VERY TIGHT ON THE ACFT IN FRONT OF US; SO I INDICATED TO THE CAPT THAT I THOUGHT THE SPD WAS GOING TO BE MORE CRITICAL THAN THE ALT AND THAT HE SHOULD PROBABLY TELL APCH CTL WE WERE PROBABLY NOT GOING TO MAKE THE ALT RESTR; WHICH HE DID. JUST ABOUT THE TIME THE CAPT WAS TELLING APCH WE WEREN'T GOING TO MAKE THE RESTR (13000 FT; WITH ABOUT 4 MI TO GO); AND THE RATE OF DSCNT SLOWED CONSIDERABLY FROM WHAT IT HAD BEEN; WE RECEIVED A TA. THE TFC WAS INDICATING DIRECTLY BELOW US AT 11000 FT. THE CAPT LOOKED OUT HIS WINDOW; AND EVEN THOUGH IN THIN CLOUDS; COULD SEE THE ACFT; AND TOLD ME TO LEVEL OFF AND TURN AWAY. WE HAD NOT YET RECEIVED AN RA BECAUSE OF THE DECREASED RATE OF DSCNT APPARENTLY. I LEVELED OFF AT 12000 FT AND TURNED ABOUT 30 DEGS OFF HDG. THE CAPT PROMPTLY GOT ON THE RADIO AND INFORMED THE CTLR WHO SEEMINGLY STILL HAD NOT NOTICED THE CONFLICT. WHEN FIRST INFORMED OF THE PROB; THE CTLR ACTED LIKE WE SHOULD HAVE BEEN AT 11000 FT AND WAS CONFUSED ABOUT WHY WE WERE AT 12000 FT AND TURNING AWAY. I THINK IT WAS AT THE POINT THAT THE 'BLIPS' BEGAN TO DIVERGE THAT HE FINALLY BECAME AWARE THAT THERE WAS A PROB. HE CLRED US BACK ON COURSE AT 12000 FT AND WE EVENTUALLY GOT AN ILS APCH TO RWY 35R. I HAVE NO IDEA WHO THE OTHER ACFT WAS EXCEPT THAT THE CAPT WAS SURE IT WAS ANOTHER MD80. I ALSO HAVE NO IDEA WHERE HE CAME FROM. IT WAS NOT THE ACFT THE CTR CTLR WAS GETTING US BEHIND AS WE WERE APCHING UKW. I DON'T REMEMBER SEEING THE OTHER ACFT ON TCASII UNTIL JUST BEFORE STARTING OUR SPD AND RATE OF DSCNT REDUCTION APCHING 11000 FT. CONSIDERING THE 'WHAT IF'S' IS SCARY! IF I HADN'T BEEN CONCERNED ABOUT OUR DISTANCE TO THE ACFT IN FRONT OF US; I WOULDN'T HAVE SLOWED OUR RATE OF DSCNT AND AIRSPD APCHING DAGLE AND THE LEVELOFF. IF THE CAPT HADN'T COMMANDED A LEVELOFF AND A TURN AWAY; WE WOULD HAVE BEEN RIGHT ON TOP OF THE OTHER ACFT. IF WE HAD BEEN IN THE ACFT I FLEW JUST THE DAY PRIOR; OUR TCASII WOULD HAVE BEEN INOP. WITH JUST THOSE FEW CIRCUMSTANCES ALONE; I'M NOT SURE THE OUTCOME WOULD HAVE BEEN THE SAME! A HIGH RATE OF DSCNT; COUPLED WITH NO TCASII ON ONE OF THE 2 ACFT; THE POSSIBLE DELAY OF EXECUTION FOR AN RA AT 11000 FT ('DSND; DSND NOW') FROM THE LOWER OF THE 2 ACFT; AND THE UNEXPECTED DIRECTION OF CONFLICT RESOLUTION COULD HAVE RESULTED IN A COMPLETELY DIFFERENT CHAIN OF EVENTS.