I'm not sure that this cncept of looking at the % of a formation in combat at any one time is not a bit of a red herring...a large proportion of the force will (should) be committed to reserves at each level - I think 1/9 at each level from distant memory e.g. a section/squad at company level, a platoon at bn level, a coy at Bde level etc - that's a lot of troops when you roll them all up but I don't think it's correct to say that they are necessarily 'out of combat/contact' and thus not necessarily out of the span of comamnd equation.

I'd argue that the NZ Div on Crete and at Minqar Qaim was pretty heavily committed, as was pretty much every airborne div immediately following a combat drop in WW2...