Min, Max and Everything Inbetween.

So, just been looking through my Skitarii and Cult Mechanicus books, as I'm looking to shape up my existing forces so I have the option of fielding some formations.

These are new to me, you see, and I don't have a great deal of experience.

And what strikes me is that they don't all need a large investment of points. For instance, Numinous Conclave can be fielded for as little as 360 points, yet can max out at 2,160....

And I only picked that one because it was the one I last looked at.

Can anyone offer a vague ranking of Formations, and perhaps discuss the 'sweet spot' for each?