Just finished assembling my 720t cargo T-9 the other day and took it for a spin:
Source: https://youtu.be/qE12qcu_15s?t=190
Further encounters at 6:30, 10:50, and 16:00. Keep in mind I just put that ship together and this is my first time flying it since the 3.0 beta, and my first time fighting an interdiction, or actually looking for combat in one, ever.
The handful of missions I picked up at the time didn't spawn many high ranked NPCs, but I never encountered an interdiction I wasn't going to beat (and I'm not particularly good at the tunnel game, so I always submit to any CMDR interdiction), including that initial one from the Elite vulture, and had to submit at the last moment when I was interested in actually testing the ship in combat.
Will max out the cargo capacity later on some Elite missions so I get 1-2 high rank NPCs at the same time...but I don't expect even two Elite NPC anaconda mission target in the same instance to really pose a serious threat, and since NPCs can't win an interdiction even against a T-9, unless I submit, the combat is still entirely optional.
My thoughts from Dec 2016
The problem isn't what CMDR's have, it's what NPCs will not and cannot do.
They are just as dumb and just as passive whether my CMDR is in a completely unEngineered Viper III, or his every-module-maxed-out FDL, Krait, or Corvette.
Take a wing pirate assassination mission by yourself. I think it's hard enough. There were times when I was stalemated in a good M size combat ship like the Chieftain and had to get my Corvette to actually finish the mission without the chance of the target running away first, or me having to run because I was getting swarmed.
Threat level 6+ npc encounters can be harder than some players.
Wing assassination missions can be a challenge for a medium vessel, but it's still something one has fully opt into. You will never encounter these targets unless you go out of your way to find them and when you do force an encounter their behavior is still highly formulaic. A big problem with difficulty is how NPCs are only reactive, rather than proactive, so NPC encounters are always on the CMDR's terms.
Since none of you appreciate MoM's genius
The problem isn't with SJA, it's that she has her hands tied and has to work within limitations not conducive to providing an immersive or persistent challenge.