I think there are better ways to implement progressive content than to buff NPCs without telling anyone so they present a new unforseen challenge, especially in a game where death has actual consequences beyond respawning in a nearby graveyard.
Also, a straight HP buff to NPCs is not exactly impossible to work solo builds around. It took someone in our group less than 2 hours to come up with a workaround solo setup for killing the Serpentis Agent that is basically better in every single way compared to the old setup, and our solo fits for the other agents are robust enough that they still clear their respective agents just fine, if a tiny bit slower.
Edit: Oh yeah, and for the inherent risk involved in these missions, I think the reward is well justified personally. I still lose ships to these missions on a weekly basis due to my own mistakes. And I work in null-sec, you wouldn’t believe this but I easily lose more ships to the rats than to campers/roaming gangs out there, it’s just a testament to how deadly and unforgiving these rats already are.