How many miners can a miasmos hauler keep up with?

Up to 15 or 20 belts, yes. Just make sure your looter timer is long enough to get through all belts, including time spent looting.

If its in tank group will it not warp to belt where group is instead of checking all belts?

Then it would support 8-10 I'm guessing.

cippy wrote:
If its in tank group will it not warp to belt where group is instead of checking all belts?

Be mindful that unless you're using a networked tank mode (still in beta), you're going to lose a LOT of yield by having the looter running on the same system as the miner; the looter's processes take a while to perform, it leaves your miner clients idle for considerable periods of time. I saw a difference in 30-40% when I moved my Hauler into their own VM. The Miasmos is fast enough to go between a large number of belts, as long as you keep the reactivation time low, keep your BMs well-centered in the belt and you use tractor beams to minimize looting time.