If I did my math right you can do a level 4 mining mission (the “hardest” requiring 45,000 m^3 of ore) in about 2.5 minutes.
The Rorqual mines about 18,400 m^3 a minute (in industrial core mode).
If you are using an industrial core, the module forces you to be immobilized (and can’t warp) for 5 minutes while your active. Also the Rorqual isn’t the fastest ship to align or warp speed. So that would stop you from rushing these really fast.
Also I just realized that Rorqual’s can’t dock in NPC stations and only L to XL strucutes. So this would mean you would need a structure to dock your Rorqual and a hauler.
Needing to haul all that ore from one place to another (if doing solo and singleboxed) would probably add another 3 minutes.
I think overall doing a level 4 mining mission with a Rorqual would take around 10 minutes. Which I think is on par with the time it takes to rush through a level 4 security mission (not getting loot and salvaging).
So it isn’t any faster to do. Doesn’t pay better. Doesn’t provide as much standing.
This is just based off my bad math, so this isn’t definitive. But doesn’t seem that mining missions with a 4 bil ISK ship is worth it compared to just mining regularly or doing normal level 4 security missions.