[quote=@Sierra]
[i]How will other players be interacting with those factions beyond just annihilating them?[/i] 
[/quote]

The Lucifern Hosts aren't a mindless horde hell bent on consuming everything. They are still capable of trade and diplomacy (although they will have a different outlook on those). They don't want to conquer everyone outside of trying to get at that space elf goodie bag like everyone else, they kind of realized what happens when they tried (re: got their shit kicked in hard).

They still have research, they still look to colonize, they still seek to expand and they still do mostly what most other empires do. And because there's still a decent number of people who have independent thought you can still do 1 on 1 diplomacy and intrigue. In fact the hive mind is a double edge sword because while their own thoughts aren't really private so they can't hide things, its a lot easier to convince the lot of them to go and do something since you only need to convince a small number of people to have the collective conscious lean that way. In addition there's still delegation of power (think like a synaptic node) so some groups can still go rogue/have different ideas. The hivemind just makes it a lot harder for them to actually try and kill each other over it but they can just "ignore" the other.

This degree of independence means that trade is still possible, even if for just luxury resources because they still have wants and still want to show off and still want the finer things in life. Even among the lower masses of drones, there's still those who have skills that can be expressed like artists. Plus they don't just use biomass for everything; they have a biotic component to a lot of things but still need technology which means they still need researchers, still need builders, still need miners, still need all the things you'd need to build ships and factories and cars and stuff.

Hell, the virus can't even naturally reproduce, it needs host either in new life or new corpses. It can make like really small creatures out of pure biomass (think like Tyranid Rippers) but if they want anything that's actually sentience and useful, they need bodies. There's actually a whole culture around "introducing" the virus into younger people at various points in their lives. Think like age rituals or coming of age ceremonies.