I fully appreciate the need to patch severe security issues. However, I was not involved in any discussions on them, so my knowledge is somewhat limited.

So involve yourself in the development process? You don't need to know how to program, just reading over large issue threads to give your own curated view of participants posts could help steer development.

Was it not possible to fix these issues without adding another level of difficulty for new miners?

No, the priority is to establish a secure network to which once the dust has settled we can analyze the true staking reality (everything is speculation right now) and react appropriately once other high priority dev items are out the way.

Or was this a temporary measure on the path to making a more balanced reward system?

Network security has been prioritized over staking priority for POR crunchers, there are multiple proposals for improving the POR mechanism which are publicly documented on github (wiki).