One last note about clean vs dirty space. Yes, the game gets cluttered. You do however get a number of clean shots in each turn. That's why the comparisons noted have been clean space, because the Carnages would be fired first, as your primary gunships. Lances are great support guns and so lance-boats are support ships.
Towards the end of the game you may not be guaranteed clear shots. However at this point you'll be at closer range. All you have to do is avoid the furthest right column against 5+ armour and the next column in against 6+ armour, but even this last one isn't that bad (comparison against variant Murder), dropping only 1/6 of a hit when not locked on and gaining parity if locked on.
Yes, Carnages are generally in squadron. In larger games you will have more than one target and so get more than one clean shot. This can be from another Carnage squadron or maybe just improved performance from another ship or squadron (perhaps a Vengeance or the fixed Despoiler for example).
Forming squadrons is beneficial for increasing chances of LO as well as combined firepower. On the other hand the MMH combination so often favoured has no reason to squadron beyond trying to hide the Hades. The Carnages being on your back lines and abeam are quite resilient, whereas the MMH squadron will take a pounding, so take a huge amount of damage or brace and lose a lot of firepower.