SYN FLOOD PROTECT killed my network

RouterOS General
1

Internet stopped to work, or very slow. Latency went from 5ms to 1000ms. Many times not possible to get into winbox. CPU was not 100%.
I have this rule as prevention against syn flood:

/ip firewall filter add chain=forward protocol=tcp tcp-flags=syn connection-state=new \
action=jump jump-target=SYN-Protect comment="SYN Flood protect" disabled=yes
/ip firewall filter add chain=SYN-Protect protocol=tcp tcp-flags=syn limit=400,5 connection-state=new \
action=accept comment="" disabled=no
/ip firewall filter add chain=SYN-Protect protocol=tcp tcp-flags=syn connection-state=new \
action=drop comment="" disabled=no

but seems it make it worse…Only after disabling this three rules, everything seems to run normal. Why? can anybody explain?

2

Here is written that there is better way not tu use DORP, but only reject in Firewall. What you think about that?
http://www.chiark.greenend.org.uk/~peterb/network/drop-vs-reject