but how will the romans even know if the legionnaires are dead? i'll answer for you: they won't! they'll get news back that 'the dacians have sacked the town, longinus is presumed captured' and that is all
The Romans can tell from either the corpses, from some Roman patroll who witnessed the event from afar or more likly from their spies in our cities who will report this to their employers. Also the Romans might consider re-use their turn-coats since they might give them an advantage, as well as weakening our position. Or the auxillaries will just make it for the hills if they feel in to much danger while the Romans cuts us to pieces.

Also, insteed of trying to have our men spend time training raw recruits who will anyway never be equall to the Romans in numbers, quality or equipment I do belive that to use the time untill the Roman launch their invasion more productive will be of greater use. The training can be left to the traininers who do train people for a living. Anyway, town milita arn't to be employed in the field, loss of life for no gain. Or more like it, mouths that eat and drink without arms to fight. Insteed better quality troops, mercinieres and allies from people who are traditional enemies to the Romans should be focused rather that pure masses of sword-fodder.