Hmm, just stating what worked for me, But I'd rather stay out of that overloaded forward beam array arc. Is he using some 'odd' skill like torp spread or something ?
I seem to remember an early encounter in the story arcs where one has to put down a D'deridex in lvl30 ship (mine being a BoP). IIRC I had to decloak on his rear, unload and bug out, and repeat. I couldn't get closer than 5km because of the torps, but they are slow and easily outrun. At the time I was running a pair of MkIII ppl. DDC's and a photon torp.
...And the rear shield is ALWAYS the weakest in every other trek game I've ever played, it's impossible to tell in this game as the shield power is shown in percentage on the HUD. There's NO possible way someone would design a ship for frontal attacks and give the front shield the same power as the shield furthest away from the assault.
The OP complained about torps, I replied w/a way he can avoid them (some sci abilities too). NPC energy weapons are a joke for the most part even w/BO, most encounters just require chaining EPTS w/TT. That said, w/e works for you.
Btw, you're making bad assumptions regarding shield HP distribution. Every player ship has evenly distributed shield HPs across the 4 facings. I've never seen anyone present any combat logs (the way you can tell if you really want) to show NPCs are any different.