RAW table supports the ability to filter only for input chain if you want. Use dst-address-type=local. That’s what input chain does, except RAW is before conn_track, and input is after.
If you completely use only RAW table and therefore your router is stateless, even a 20G multi-gigabit DDoS will not cause the router to crash or reboot. But start using conn_track and good luck on a DDoS attack.
But as others have stated, RAW table is meant for advanced users with in-depth understanding of iptables + various RFCs for best practices. Randomly using some “Drop the rest” rule will also break all traffic initiated to/by the router such as BGP peers etc. You need to truly understand the Netfilter packet flow and logic.
You could follow the firewall rules here for raw filtering on the edge while not breaking any RFCs:
http://forum.mikrotik.com/t/how-to-edge-router-and-bng-optimization-for-isps/150007/1