I think this plane should have dumped fuel in the Atlantic and landed somewhere on the east coast for repairs. Considering that they didn't know for sure that the problem was isolated in one engine, it was reckless to continue on to Great Britain.
Considering it took off from LAX it started out over the Pacific. In order to dump fuel over the Atlantice, it would have to cross the US first.
The Miami incident was an emergency landing. I not sure if they got down to the recommended maximum landing weight or not. They didn't have much choice, because the engines weren't going to last very long.
Considering the flight path was going to be over land for the first few hours anyway, why dump fuel when it could be burned off enroute to an alternate destination where the passengers could be switched to another plane? The other three engines seemed to be working fine. It would seem to me that flying over the continental US with three engines working would not be very risky considering the number of airports available for diversion if necessary.