Say I have a Hunter Contingent (the Tau 'decurion' style detachment) comprised of Hunter Cadre and an Optmised Stealth Cadre, will this count as one detachment against the ITC tournament limit of three detachments? Will I be able to add a formation detachment with a Riptide Wing and an allied detachment with an Assassinorum Operative?
“Decurion Style” Detachments comprised of multiple sub-detachments count as 1 detachment towards the 3 detachment limit.
A new edition may render this answer obsolete, but until then, this is the official ITC position. Including full text for posterity:
An army may duplicate a single Detachment, one time.
Example: A list may include 2 CADs, but not 3 CADs. Or, a single CAD, and 2 Allied Detachments. Or, 3 Formations, 2 of which are the same Formation, etc.
This includes “Decurion Style” Meta-Detachments which are comprised of multiple datasheets and Formations. They may only take a single duplicate Formation, one time within the Meta-Detachment, although they make take duplicate Data Slate units within the Detachment if permitted to do so. Example: Necrons may take the Decurion with 2 Canoptek Harvest formations within it, but no other duplicate formations.
Note: “Decurion Style” Detachments comprised of multiple sub-detachments count as 1 detachment towards the 3 detachment limit.