I don´t think that main issue is QGJ nerf. Sure, they knew how powerfull he is through the leaks and honestly, it really felt like a bug. Main problem is lack of communication. They informed about his neft after many people used him in Grand Arena and lost because of this. This is what i found inexcusable...
Anyway, CG needs to refund not only his zeta/omicron, they should also refund any materials above relic 3 which are the requirements for Jedi Master Kenobi. If this happens (and it really should), i will probably upgrade him again, but people should have choice. They paid knowingly for something else and it was taken away from them.
PS: People should also get refund for Grand Arena issues. Leader of my guild lost a whole round because of this and he wasn´t only one.