Let me put things this way- if you can mount 2x Mjolnirs, you could mount a Storm Needler and a Hephaestus Assault Gun and it would do more dps to armor and shields than the Mjolnirs, but for ~2/3rd the flux cost. Even replacing the Storm Needler with a Mark IX Autocannon, it would still be better in just about every way.
@ flux cost
unless you're using it on one of the low tech vessels(which you really shouldn't), it's fairly moot since you can augment the conquest to dissipate far faster than it can generate, even with the mediums firing i have very little buildup in my setup, so i don't see why cost should be a consideration factor when it can be made moot.
moot.
@ the DPS
2x mjolnirs = 1066
1x Storm Needler = 1498 (shields)
1x Hephaestus = 960 (armor)
combined(armor) = 1049
1x mark 9 = 696 (shields)
1x assault gun = 960 (armor)
combined(armor) = 1001
1x hellbore = 1000 (armor)
1x gauss cannon = 700 (shields)
combined(armor) = 1042
so yeah, the only weapon that really beats it is the storm needler.
but they are so close together that unless you -really- need that extra few damage, you can pretty much go with any combination you'd like.
now, as for my take:
every other weapon (minus the assault gun) offers expediency, which is extremely valuable in large ship combat since it vastly lowers the damage your fleet takes thus letting you be more aggressive in the field. i think this is why the mjolnir feels bad, as it's basically a "chip away at the enemy" weapon on either a relatively fragile platform (the conquest) or being used on vessels that really can't use the thing (all the low tech ships).