My mining fleets come in three basic variations:
Yield Fleet: 4 Hulks; 1 Field Orca; 1 Field Freighter (Charon); Sec status systems: .9 and 1.0
Tank Fleet: 4 Procurers; 1 Field Orca; 1 Field Freighter; Sec status systems: .5 through .7
Mack Fleet: 4 Mackinaws; 1 POS or Safe Spot Orca; 1 Freighter or Station/POS; Sec status systems: .8 through 1.0
There is no perfect choice. Each has pros and cons concerning risk and yield. Generally, I won't use Hulks or Mackinaws in systems with a security status below .8 because they are at higher risk of being ganked. Tank fitted Procurers in .8 or higher is tanking overkill. Macks are my specialty fleet - I use this setup on mining clean-up ops where I'll send them to different belts for leftovers before downtime.
Other variations include friends joining the fleet with non-doctrine ships or fits. I'll let pretty much any mining vessel into the Yield Fleet and Mack Fleet (though I doubt I'd accept Covetors/Hulks into a Mack fleet). Tank Fleets require Procurers, period. Skiffs would be fine, but in my opinion they're pricey overkill.
By "field Orca" or "field freighter" I mean those ships are actually active in the belt with the miners, as opposed to sitting in a POS, at a safe spot, or within docking range of a station. My Orcas are usually fit with two T2 Mining Foreman Links (Laser Optimization II and Mining Laser Field Enhancement II) and the T2 Siege Warfare Link - Shield Harmonizing II. They are heavily tanked (DCU II and Reinforced Bulkheads II in the lows; four shield modules in the mids, and three shield rigs). I do not use a tractor beam. Instead, I carry a Mobile Tractor Unit in the ship's cargo hold for use in those belts where the mining vessels have to spread out a bit to get the last asteroids, sometimes in opposite directions (the opposite ends of the belt horseshoe).
I'll sometimes swap the freighter for a second Orca in the Tank Fleet. The Orca costs less than a freighter, can tank better than the freighter, and can provide other services, such as Armor and Info Warfare links and a tractor beam instead or sometimes in addition to the Mobile Tractor Unit. Certainly more warping than when using the freighter for storing ore on the field, but a tradeoff worth considering in .5-.7 systems (especially .5 and .6 systems known to be frequented by gankers - but then again, why mine in those hot systems when there are so many other choices?).