PHOENIX PHIL
AH ambassador
You could just take BA from DFW and not worry about changing airlines at Heathrow T3 to T5. I will be taking BA from IAH this summer, of course I have to drive to Houston from San Antonio, the Austin flight is just too expensive and impossible to get miles seats on. I would have loved taking the DL flight from ATL, but Business class was too expensive, so I opted for BA Premium E, The Delta E product is just not that good, even paying the extra for their idea of plus, not for that long of a flight. I also look at the Emirates flight from DFW Business and was serious considering taking it over the BA, but maybe net time.
By the way you could use those miles on QF and fly to OZ direct from Dallas, that's a very nice flight in premium E on a 380. Or head to IAH and take the direct to NZ of course no AA miles for that flight.
I took BA to London from Phoenix last summer. Didn't have to change terminals, was T5 the whole way. A bit of an inconvenience having to redo the security tour though. Biggest beef I had doing this was we flew on 747's. But if I had the air miles to use for tickets, I'd do it again. And/or if the flights were significantly less as they were when I got those tickets. There is a slight hassle with paperwork for the rifles, but not a big deal, that actually made me feel like my rifles were in better hands than just any old ordinary luggage.