I remember this mission being hard, but I've played through it seven or eight times now, and I can't dock to the station without being destroyed. I can take out two spider guns with the remote probes, but that leaves four, and even one is enough to slaughter me while the auto-dock flies me 5 klicks from the station. Any tips? Are there two particular guns I should take out? I've also tried using the disruptors to disable the guns while I dock, but the effect only lasts about 5 seconds, and the autopilot takes longer than that to dock.

Yeah, this mission really was a pain in the back ;)
Try disabling as many guns as you can and activating the autopilot when you're a bit more than 5km away from the station. This way the ship should head directly towards the station instead of getting away from it first and then attempting to dock while being shred to pieces ;)
Boosting power to your shields might buy you a few extra seconds too. Just leave some power to the engines as well or the ship will become very sluggish and the docking procedure will take much longer. However you can cut all power from guns since you won't be using them anyway. In case you don't know you can set power distribution with ctrl+arrow keys.

There must be another way to do this mission other than just taking out the 2 spider guns, then trying to dock and simply crossing your fingers?

It's the only mission on Defiance I've had any real trouble with so far. I'm boosting my shields, taking out the 2 spider guns that are closest to the station, and then auto-docking from an angle where I shouldn't autopilot through the remaining gun's fire arcs - but they always kill me nonetheless...

The trick to this mission (according to some hints I wrote many years ago) is to get the spider guns to shoot eachother.

I got that you were meant to recon probe two of them so they'd switch 'sides', but hadn't figured out to hover behind the remaining guns so their buddies would accidentally shoot them while going for me. Then it's just a case of boosting the guns and point-blank rapid fire PBC until they're all dead. Easy if you know how!

I had similar problems with the COSA mining rig in the next mission - if I had one criticism of Defiance it'd be that sometimes it's not clear if it's possible to damage some of the unique bigger ships at all until you read a walkthrough - the main I-War campaign conditions you to think if something doesn't show damage from a few PBC hits, it's scripted as being 'immortal'...

That said I'm loving Defiance, the missions are great, and it's completely bug free compared to the Navy campaign. 2 missions to go then I'll start on IW2 for the first time!

It's a different game, but I think also very fun. A little less simulation and a little more arcade, but you can play it with full newtonian physics. I think the management is much more streamlined; the only thing I think is really removed is the repair aspect of the ship and ability to shoot 360 (which granted is big) degree rather than mostly straight out front.