I wonder if the issue was something they worried could be exploited (because the server was getting attacks against a target that no longer existed and was actually applying the damage) and that was why they didn't publicize it before a fix was made. I also wonder if they weren't sure if the fix they implemented would resolve the issue (they might actually not even be sure yet) and that's why they didn't mention it in the patch notes. It's possible the danger is still not past and the only reason they have commented at this point is the outrage. They've declared that they want to be as open as possible about their fixes for hydra and hydra clash, but their actions have been the opposite to this point. A good honest "here's what we see as the legitimate problems right now; here's where we want it to be; here is our current timeline for resolutions" would go a long way, at least for me.
That would be an improvement. However, you will never get anything close to that level of transparency from Plarium.