Now days a decent grief ship can destroy a trader completely in - literally - a couple of seconds. Maybe if FD has stuck to plan a with ships being hard to destroy but expensive to repair the problem of ganking and griefing would be more of an annoyance?
Maybe they should go back to that?
I think the first problem was well-embedded once frag cannons and pacifiers were introduced in version 1.3. They're a well-balanced weapon against a reasonably outfitted target, but versus a soft, slow, large target they're deadly. Though, that said, one of the main reasons that PvP hostiles weren't as big a deal in 1.0 is there were just far fewer pilots about in total - probably less than a tenth of the total sales - so people just met them less often. CGs-as-hotspots didn't really get going as a thing until long after Powerplay had broken down, Engineers-as-hotspots wouldn't exist until 2.1, and too few had the Shinrarta permit yet for it to be a really busy system either.
Engineering has actually made things better for the trader - if they choose to make use of it - by allowing them to get ridiculous defensive levels with minimal compromise to trading ability, so they can basically escape with ease. But, they don't have to make use of it, and enough of them don't that there's a supply of targets.
High repair costs isn't going to help, though.
1) Once repair costs get above 5% of value, you can just self-destruct to get them done cheaper, which is what people were doing in 1.0 before they brought the costs down. But 5% isn't a major expense on most ships compared with what those ships can earn. (And making the base rebuys more expensive would have its own issues!)
2) The majority of health on a modern ship is shielding - which means your repair cost for escaping is usually zero anyway.
Consider that in this game you can rightly complain about bigships being instagibbed, and simultaneously about the same ships built differently taking upwards of 20+ minutes and several ammo synths to kill.
Yes. There's too many different types of matchup possible to balance this well. At the moment the toughness is reasonably good for a 4v4 wing-fight, but 1v1s can last forever (literally, in some cases) - but bring the toughness down so that a 1v1 is reasonably quick, and a 4v4 will be over very quickly too.
Similarly with escape times - make it possible for an underequipped trader to escape, and there's no point whatsoever in trying to PvP bounty hunt a ship that actually has decent shields. Make it possible for that PvP bounty hunter to succeed and even a prepared and engineered trader will be in serious trouble.