I may be new at these forums but I've managed to beat him every time with a Negh'var loaded like this:
Disruptor IVF's on forward-firing primary hard points
Photon torpedoes on forward-firing heavy hard points
Type X shields all around
Type X warp core
Type I (you read it right, I) thrusters
Best impulse that will fit
Type V computer
Nothing on other hard points
This works with a strategy I've seen called the Kaufmann Retrograde. In this mission, that means that you go in, go to red alert, reinforce your forward shields, face toward Jureth and head straight at him until the hails between you two begin. Once the hails start, throw your ship into full reverse, Jureth wil come right toward you. Move your power sliders to maximum on both primary and heavy weapons ( this is why you don't have any weapons on the arcs that don't face forward, they'll just suck up energy), turn on your scanner (I swear that it improves weapon accuracy), and shoot him as soon as he comes into range, and as often as you can after that, make sure that you are targetting his hull and keep firing even after he says that he's going to blow himself up, because he'll keep shooting at you. This has worked on Commander difficulty after the patch, but I haven't had a chance to try it on any higher difficulty yet, as I'm still plodding through the Romulan campaign. It isn't the only way to beat him, just another suggestion that has worked well for me.