My formula (which is available on here somewhere) turned it out at 392.5pts, reason being it isn't actually all that heavily armed.
Shields and armour came to 138.6pts.
Speed and turns came to 14pts
Turrets come to 18pts
Lances came to 148.7pts
WBs came to 28.1pts
D3 Nova shots ~ 2 Nova shots ~12 torps = 44.8pts.
The dorsal armament is weaker than a battlecruiser. The lances may be nice at long range, but twin long range broadsides have poor synergy with each other and don't come anywhere near the BFG:R Retribution broadside in damage potential. The only seriously nasty weapon on the thing is the D3 Nova, and personally I'd prefer 12 torps.