Without the BMS you have no protection from high or low battery voltage, high or low cell voltage or high or low temperature. Therefore you are at risk of damaging your battery and rendering it useless.
You should assuming you have a simple system add a small BMS and a Smart Battery Protect to isolate your loads on low voltage. The Small BMS can shut down the Orion on overvoltage or low temperature via the remote connection. Go to the Victron site and check out the different BMS options.