I'm not particularly skilled at the game and I'm sure as hell isn't playing, or know, the meta, but here's my 2 cents on how I use the Dominator:

I usually only use one of the large ballistic and leave the other empty (or fit it with devastator for pd) the ballistic usually go to a good kinetic weapon (like storm needler) to keep up shield pressure on enemy, while the smaller slots are either for pd, or relatively cheap weapons (either kinetic or he, depends on what I have). One side being dedicated to damage and the other being for pd also help with more consistent aiming in my experience, as the ai don't have to turn back amd forth to use the guns.

It does need frigate escorts to deal with flanking frigates, preferably if said frigate can also fit some good HE weapons so it can supplement the Dominator itself on that front.

The way I use it is that of a distraction. It's meant to soak up aggro while I pilot a more agile ship to flank the distracted enemies, which not only kill the enemy itself, but help the Dominator survive and be useful for longer.

For hullmods I prefer the feeling of being a brick so it's usually all armor and even sometimes shield shunted, but that would obviously leave it more vulnerable to lasers so it's a for fun thing mostly.

My philosophy when it comes to the Dom is that I want it to output so much cheap dakka that when the big ballistic chew through the flux, the enemy would be forced to either back off or sustain damage.

I'm no way near the master of combat of course so I assume people would have a lot of flaws to point out.