The Doomtroopers don't seperate from the squad, as in FFT, they just don't have any sort of Command Distance coherancy. It is spelled out in the "Doomtrooper Pairings" paragraph before the DT troop selections. Unfortunatly Thom was a bit wordy when he coulda just said, "the Doomtroopers do not have to maintaint Squad Coherency".
-PFC joe