Not a lawyer, but I can see why a lawyer would go after RR and not QF...
I would suspect it is because QF was operating the engines within manufacturers specifications and in accordance to all maintenance schedules as put out by the manufacturer. It is this reason why I suspect QF was able to claim compensation from RR in the first place.
Had QF not followed the instruction manual to the letter I would suspect that QF would also be a target for such lawsuits. However it's a little hard to go after a company which is using all reasonable care in the operation of equipment not built by them.
Far from a lawyer here either, but my two cents...
I don't think many will see it like that.
At least in OHS terms, most people would understand that employers ultimately have vicarious liability. That said, when brought to court, it may just be ruled that Qantas does not deserve apportionment of the blame and hence the case would be thrown and proceed to the next liable target, RR. However, to have such a case thrown is not trivial (but that's a consideration on both sides).
Anyway, from the article it seems this case has been "baking" for a while, and only come to a new head now. I really wonder how the plantiffs are going to prove negligence on the part of RR, particularly if the damage is trauma and stress (rather than a more standard physical injury of sorts) - not that those kinds of damages are insignificant at all, but they are difficult to connect causally in court IMO. It'll be interesting to see what damages are being claimed. It'll also be interesting to see if RR will come down hard on Qantas exec for not curtailing such action against them after they have paid massive compensation.
I love also how the legal company representing the class action has proudly said they are taking on the case on a "no win, no fee" basis. They probably didn't mention that if the class action succeeds, they will take a massive cut of the payout. Also if they lose, there's no legal fees, but who will pick up the counter costs? Maybe it's a bit of journalistic creativity, but this is anything but altruism.