If you're unfortunate enough to run into the erroneous PBC hit detection problem, the game isn't just insanely difficult, but pretty much impossible...

I couldn't finish even the WEP Advanced mission, until I managed to get the hit detection workaround. After that it became just difficult, but doable.

There still are insane moments mind you, like when your wingmen in Neutronium Galore suddenly start to attack you or each other. And then your character complains at the end, if only he could save those crews...

*sigh* It's a good game, but buggy. And those bugs stick out even more on fast modern machines.

Anyway, don't forget you have front as well as rear missiles (and PBC cannons), which doubles your missile ordnance! Alas, you can only fire rear missiles on WEP screen ([F3]) - when your target is behind you (the game automatically selects which launcher is used - try turning away from the target, until a status message states rear missiles are now in use).

Presuming anyone still is still trying to finish the Gatekeeper mission (and you managed to fix the hit detection first, otherwise just forget it):

* I found it best to hang behind the wormhole exit (it really bugs me that the game calls these Lagrange points - in astronomy, Lagrange points are something completely different - but I digress). Turn your back toward the wormhole! That way you'll use up rear missiles first and keep the front ones for later).
* Switch to WEP screen.
* Switch to Ripple mode ([F]).
* As soon as the enemies appear, lock the closest one with [R] then start firing missiles. Two or three per enemy should soften them up nicely and the gunstars should also add their fair share of damage. If you're lucky, there will be fewer enemies already before you even start the engines and start dogfighting them - and even if none is gone yet, they should be pretty damaged anyway.
* For the next wave, if you run out of rear missiles, park behind the wormhole facing it and use the front ones of course.
* Use WEP screen for dogfighting as well (lock the view forward with [Right Shift]) - that way your gun will swivel much further and hit your targeted enemy anywhere on the screen (or even behind you), not just a few degrees around the center!
* Use [F9] to lock your speed with enemy, then use [A], [Z] and lateral movements to change your relative position to it.
* Set joystick's hat to Lateral movement. Makes it easier to dodge enemy fire (and to get under its softer belly) during dogfighting than using the [S] key.
* If your hull is still at full strength, you can ram enemy ship to quickly damage/destroy it. Just prior to ramming it, hit the [Insert] to ramp up your shields for a second.
* If you pick up too much damage, use LDS drive to run away for a while.
* Stick around gunstars for cover fire. They cause way more damage to enemy ships than your own gun.