I agree with OP. Combat is too easy.
However, instead of simply cranking up the difficulty, I'd prefer if things just made more sense.
1. As OP said, no shield-less novice easy-farm pythons and anacondas. Bigger NPC ships should have some minimum rating.
2. Higher-rated cheaper ships should pose danger. At the moment elite NPC sidewinder poses as much danger as harmless NPC sidewinder, just takes one more second to kill, when a good sidewinder should take some time to kill one on one because of its maneuverability.
3. Implementing above, bounties should be adjusted to accurately reflect ship's power. Maximum bounties should be increased for biggest highest-ranked ships.
4. I'm not sure cell banks are balanced. I think they make farming NPCs too easy and generally make PvP worse.
5. Different systems should generally have some consistent average difficulty, and it should be possible to determine it from information about the system. So that people who want to hunt bigger ships, could find them without going through hordes of sidewinders.
6. NPCs should sometimes fly in groups and use wolfpack tactics when attacked.