Thanks for your answers Scream and Primarch.
At least it shows I am not the only one a little unsure how to read the rules for the unique formation. If unique disallows one to pick the unit in armies of less than 3000 it does not work as intented (IMO).
Unique is to ensure that there is no "spam" of the unit as I understand it. Not to prevent a player from taking a single unique formation. We often play 2000 points and with option 2 that means noone can field the unique formations. This means the avatar stays at home in armies under 3000 points, despite the rules text for him being:
Quote:
Any Craftworld force may include an Avatar. This is a Free Card and is in addition to the rest of the Eldar force, so it does not reduce the number of Special and Support Cards allowed.
After looking through the army books I can only find saim-hein, avatar, master mime and Renegade mekboy as the relevant unique formations in all the armies. So the question is, if I field less than 3000 points can I field a saim hein host, renegade mekboy, avatar or master mime?
Personally I believe you can, otherwise the rules for army building are not based on the principles of SM2 (which I do not believe has been deviated from on purpose).
P.S. I agree with Scream in disallowing a secondary unique formation at volcano with 3500 point armies as that is how they play normally. The above is purely to understand the rules.
P.P.S. I am unsure why anything besides the master mime and avatar is unique. Renegade mekboy and Saim-hein are good, but other armies have similiar good options, but that is a very biased and personal opinion.