The Taurhai

[The Tatterdemalion King]

That has to make me wonder, is their a darker side to their "paradise". Maybe reeducation camps or something like that.

By hook, or by crook...

[spshu]

Just took a look at Way of Dera the way they are depicted there they attacked the Romulans first - and they if i recall the Romulan SRM correctly their Dragon ships were not only weired looking but packed quite some punch as well.

IMHO they are just Imperialists hiding behind a mask of a benign civilisation. Much like the Romulans they treat everyone else as an inferior.
Lastly the Taurhai are just a easy explanation for the Romulan absence in Alpha Quadrant affairs for nearly 50 years after the Tomed Incident.

I think the Husnock works better as they were wiped out by a Douwd in a TNG third season episode, The Survivors.

[Captain Otto]

Well you could use the Husnock any way you like them to, there is almost nothing known about them safe what the Douwd who killed them all told Picard (Pretty pointless "-They killed my wife and i think they were all evil, so i killed them all in a single mad moment with just a thought).

Wait a Sec... Mental note for a Time Travel Adventure: Probably a Test instigated by Q who wants to find out if the crew is willing to accept the Douwds explanation or judge for themselves. During the Course of the Adventure it turns out that the Hussnock were worried about the Federation and in their mind wanted a strong Position to start negotiations with e.g. taking the Colony Hostage for Information and some "bargaining chips". Due to unfortunate Circumstances the Situation Escalates and first all Colonists perish and then the Douwd eradicates the Husnock in retribution.
Time for some moral dillemma. The Test also could feature Picard accused by Q for not punishing the Douwd for his actions.