Look at it another way. The plane took off and lost an engine. It can't
land immediately because it is too heavy.

My understanding is that you CAN land an aircraft overweight, but it then
has to be inspected according to a specified protocol - obviously if it's a
high 'g' landing then damage is far more likely to result - if however
(perhaps due to good conditions and a touch of luck) you land with a real
greaser then it's unlikely to physically damage anything.

Anyone have more of an insight into this? - I'm also thinking of the
Swissair 111 fire where the pilot delayed landing because it would have
meant landing overweight - and could possibly have made a difference.

My 10c worth on continuing on 3 engines is that it's not 'unsafe' per sec,
but it means pushing ones luck a bit more. If it came down to only a
financial decision, I'd have circuited to land after dumping fuel.