There are only two questions (ever)
1 was it safe? well it wasn't unsafe because (on this occasion) it didn't crash..............
2 Was it legal....NO it wasn't and that why they have been fined (not enough in my view)
There is a world of difference between flying back to base with a nav light out (that might under the MEL) deck the aircraft and setting off accross the pond with the aircraft in this state, the pilots might have had to work a little harder (what a joke) what would have happened if they had lost a donk mid pond, and Globespam and their sub lease have had a few donks die.
Xyears and 20k hours puts you nearer the one that will kill you, after that amount of time you ought to know better, but who am i with only half that time!!!