Dee Vee
There are operators involved here as well as the airplane maker. It's there problem when it goes tits-up. So no, RR isn't playing it down, they are responsive to the end user and regulator far before you get on a plane..
As for sufficient testing ? it takes years to illustrate a wear out mode failure and to accommodate this all engine manufactures follow the same protocol in running engines very hard for hundreds of hours before they are certified, so no short cuts here.
From the millions of hours of industry wide experience on all engines, a turbine blade failure condition is typically classified as a minor failure condition, it's only when two engines may get involved that it moves up notches.
The rate at which a fix gets incorporated is driven by the safety aspect and the operator's ability to absorb engines out of service. All RR can do is throw money at it beyond assigning engineers to work the job.
Yes the issue is that after 2 years we are still experiencing too many failures $$$ and pushing the risk of 2 engines so back to the snake pit of more pain to both RR and its operators
At this point the data certainly doesn't indicate that this problem is so far out of hand that a catastrophe has risen to the top of the inherent risk of flying.