I had 7 mining ships in a fleet, all 7 have 2 of the highest level mining module that mine at 14,400/h
I sent this fleet that should mine at 201,600/h based on the miners, or 100,800/h if only 1 module can work per ship to mine a farsu deposit of only 22,000.
Estimated time of completion is just over 1h35m, instead of 6 or 12 minutes.
Either the timer is wrong and displaying for only 1 module, or the mining action is only activating 1 module instead of all relevant modules in the fleet. If this is intended which is quite possible, I believe that should be added to the tooltip for the mining modules for user clarity.
After the discussion below, we’ve got the problem down to the timer that is used on the mining job.
The timer doesn’t account for the size of the asteroid field, and because the field and the ships won’t update their inventories until after that timer runs out, it appears as though you are mining at a much slower rate than you are. To benefit from multiple mining modules, you have to manually stop the job to allow for an update.