I don't have a problem with the quality of the NPCs' ships and flying. Sure, if you're in an engineered combat ship you can plow through individuals easy enough, but if you're an experienced combat pilot in an engineered combat ship that's not surprising. As stated above, you want a non-xeno combat challenge? PvP some willing CMDRs (if they aren't into it and just flee without fighting and you still kill them you're not looking for a challenge, you're ganker scum).
I do have issues wtih NPCs being able to do things that players can't.
Example: I'm space-trucking in a T9 and I get a wanring that enemies are coming. That's fine. I get interdicted by an Anaconda. Again, fine. I hold him off with a SLF, shield cells and chaff, until system security show up, and with them helping I drive him to High Wake with no shields and a battered hull. Great. My shield is slowing recharging and I'm on 35% hull, but I'm only a few light seconds from my destination and over a kilo light from the star; by the time he has jumped back into system and caught up with me again I'll have docked. Or so I thought. I low-wake and am immediately interdicted by the same NPC, who has magically repaired himself, and with no more shield cells, only a ring and half of shields, my SLF still on cool down, and a thoroughly battered hull I'm wiped out. I have to eat the rebuy, I get fined for the cargo I lost and I can't finish the delivery mission after already trucking 3 loads... and because I can't complete the mission I lose the completion bonus for killing the first anaconda that came for me on the previous leg (which was less than the bounty on a RES anaconda anyway).
All in all I'm down 20million for the ship, fines and lost earnings. I just about broke even due to the return leg mission covering the rebuy and the fine, and all because NPCs spawn wherever, instead of only at the sun like players. #salty
tl:dr You want it to be hard? Try making a living from cargo missions.
Also compare that with going mining - virtually risk free (pirates bother you once - before you have any cargo) and payout is 10x better for less or the same time investment. Talk about EZ-mode.