The two order minimum is correct for the army as a whole. If you were down to one model you'd either be in LoL and have two orders to nominate a new one or your last model would be your Lt. and you'd have his order and the Lt. order. Though straight from the wiki:
The minimum number of Orders in the Reserve is 1.
and
Remember that the Orders from miniatures in a Group are not transferable to another.
Those two statements would make me believe that you don't get 2 orders minimum per combat group one could easily fall to just one order after taking losses.