That might just be a string of luck; for me, I rarely do as poorly as average with Dilgar bolters- I've had some outrageous results, detonating WS and single salvo killing G'Quan- but designing and tinkering, you generally go with the averages.
At Battle level, we're reaching the stage where if the stats don't make you go 'ooo', there's something wrong. This isn't behemoth territory, these should be practical ships of the line, not overgrown boondoggles.
Primus;
Speed 8, turn 1/45, Jump Point, Interceptors 2
Hull 6, damage 45/12, crew 60/15, troops 5, 2 Sentri flights
Heavy Ion cannon- 24, 6AD, AP Double Precise
Light Ion Cannon- 18, F, 6AD, AP
Twin Particle Array- 8, Twin Linked, F 5AD, A 4AD, P, S 6AD
Primus Priscus;
Speed 7, turn 1/45, Jump Point, Command +1, Interceptors 1
Hull 6, damage 42/10, crew 65/15, troops 4, 2 Sentri flights
Medium Ion Cannon- 24, F, 8AD, AP Precise
Light Ion Cannon- 18, F, 4AD, AP
Twin Particle Array- 8, Twin Linked, F, A 5AD, P, S 6AD
An early command capable version, retired on the apearance of the Octurion but still occasionally found in some house fleets; it's electronics suite is notoriously difficult to keep in good repair (shoehorned in between the Admiral's harem and the Captain's hot tub, supposedly) and also tricky for reallocation of internal volume. Most have been updated to newer configuations, some remain.
Primus Novus- 2259+
Speed 9, turn 1/45, Jump Point (Adv JP after 2264), Interceptors 2
hull 6, damage 47/10, crew 66/11, troops 5, 4 Sentri flight
Heavy Ion Repeaters- 24, F, 8AD, AP Double Precise Mini-Beam
Light Ion cannon- 18, A, 6AD, AP Precise
Twin Particle Array- range , twin linked; F, A, P, S each 6AD
The Novus, or latest version of the Primus hull, was supposed to enter service ariound 2252, but long development delays held it back, and only a handful entered service in time to fight the Narn.