This is a cost-cutting exercise pure and simple. You can have all the competency matrices in the world, the results will be engineered based upon salary. If you're the bigger earner in your pool then you're gone simple as.
If you are a victim of a "Competency Matrix" wait until it has been completed and you're given a decision. If you are axed you need to understand what is the criteria and how you were marked. Get that information, walk out and go and see a lawyer. If you think it has been unfair/unjust then appeal the decision. In the UK you are legally entitled to appeal the decision.
I think every single victim should appeal regardless (subject the local law).
Bumped this into a thread from @VGa7Grd-sfk, he/she is 100% correct.