It's not really a ninja ship, it's a superhauler + compressor.
Basically you set up a POS in a nice -0.8 - -1.0 system; and you get four or five hulks stripping a belt. You have warpins to each belt at 70km radius spot.
When cans get close to 2h range, you warp rorqual in, use capital tractor beams to scoop up the cans, empty into the massive cargo bay (see setup below). Then take it back to the POS, and compress it. If the average Hulk fills a can of arkonor in 20 minutes; and therefore in a 2h period 5 hulks therefore fill 30 cans (at 27500m3 per can) this is a whopping 825,000m3. Having a Rorqual allows this to be ~8 trips and enough time inbetween each trip to compress the ore. Compressing the ore also means you can take advantage of the refiners at POSes more effectively.
Also, and perhaps most importantly, they can be used as mini-jumpfreighters for logistics work (POS setup, etc).
[Basic Rorqual]
High
1x Capital Tractor Beam I
1x Mining Foreman Link - Harvester Capacitor Efficiency
1x Mining Foreman Link - Laser Optimization
1x Mining Foreman Link - Mining Laser Field Enhancement
1x Clone Vat Bay I or a cloak (no one will seriously need a clone vat bay over the protection a cloak affords)
1x Industrial Core I
Mids
1x Capital Shield Booster I
1x Photon Scattering Field II
1x Heat Dissipation Field II
1x Invulnerability Field II
2x Cap Recharger II
1x Shield Boost Amplifier II
Lows
3x Expanded Cargohold II
Rigs
1x Cargohold Optimization II
2x Cargohold Optimization I
125,787m3 cargohold, so you can fit 4 blocks at a time in the processing lines.