I have used BA from LAD to LHR and onward to the USA a couple of times now but it was a 777 not a 767.
I agree, connections are a bit difficult at the time of arrival into LHR but in my opinion, it beats LAD JHB ATL hands down.
AF stopped the second flight into LAD over a year ago and it wasn't anything to do with BA but was intended to give TAG more flights LAD to CDG. AF now only flies into LAD on a Tuesday.
LE