The CF community is "proud" of havind the some of the most difficult NPCs in the Freelancer-universe.
What you've experienced on SP ( almost instant recovery on shields and hull ) is only a slight tradeoff for their abilities you once might expect playing on the server.
There they are able to move as in Heisenbergs worst nightmares, "tunneling" quantumphysically away from you and your beam-bolts in 45° to 270° zigzag moves just when you think a last hit will finish them off.
Meet the Crossfire NPC pilots master instructor:
@....."Is that balanced?"
Well, Crossfire is made primely for Muiltiplayer-gaming. So it seems that "balancing" against NPCs is not really an issue.
@....."Its not like the combat have gotten more challenging. I barely take any
damage, and only had to use shieldbatteries a couple of times when I got
annoyed and blindly just followed my target with guns blazing on him.
Battles arent harder, just a h... of a lot longer."
That's maybe because you are supposed to get over to Multiplay, which is quite faster ( kind of a general "gentlemen aggreement" NOT to use bots 'n batts in PvP ) and a way to get help against these silly NPCs, like flying in teams, getting the "ueberweapons" to have a chance against them and so on.
@....."So I spend half an hour flying from Manhatten to Trenton, trading diamonds for engineparts,..."
You were lucky on that one. After the next gamerestart with the "selfpatching" of the client ( if you haven't cut off your net-connection ) this profitable trade will be gone. Once a day all trading commodities and their prices will get swapped. It's a substitute for the planned and up to now not properly working dynamic economy.
@....."What am I missing/doing wrong? Do I have to spend more pointless time
flying from Manhattan to Trenton earning MUCH more cash to buy uber
overpowered ships, while still being limited to lowlevel weapons due to
level?"
When playing SP-storyline : YES ! So, in general : you didn't miss anything.
A small tip : Go play on the server, get a defender with "wreck weapon" obtainable in NY, go to huntsville-prison in texas ( when you undock mostly every time you will get pestered by Xeno-Starflier-NPCs ) and when you got pissed off by fighting them ( after 1/2 hour or so ) go back to SP.
Now you will find the NPCs there almost "delightfull".
Oh, and the easiest way ( still ) to make money ( SP as well as serverside ) is killing NPCs and selling the pod at a prison station.