Tell me I’m wrong, but for CRS3xx you should use just ONE bridge and VLAN filtering with hardware offloading like described here: https://wiki.mikrotik.com/wiki/Manual:Interface/Bridge#Bridge_Hardware_Offloading
Heres an excellent example config for the CRS3xx with separate router: http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1