mattthemuppet wrote:
to be honest though, in all those other lists Aspects are either the same price or cheaper and there are no other price adjustments that I can think of, like for like.
I don't doubt it's been extensively playtested, I've just missed all that and the arguments that went with it.
To give a quick summary...
They get as many Exarch slots per stand as Biel Tan, so there's a premium for that compared to 6-unit formations.
4-unit formations are effective as transported formations. They are tough enough to do damage but they only cost 300-400 points so they don't tank your activation count. 6 unit formations are barely workable with transports and 8 unit formations are effectively cost-prohibitive, limiting deployment options.
In air transport, they are as good as an 8-unit formation but end up more flexible afterwards like a Thunderhawk with Devs/Assault that split up after the initial air assault. They don't have the wasted space of a 6-unit formation.
There are a handful of specialty effects as well which work better with 4-unit formations. For example, keeping a single Swooping Hawk formation in reserve until Turn 3 so it can port onto objectives and screen with their Zone of Control is very effective and doesn't require diverting much in the way of assets from the main battle, while using larger formations for the same thing requires keeping more assets off the table.
Obviously, they take a hit on durability but the positives outweigh that.