I got my info from the exact same page, scroll a bit down and find this:
Did not work on VPS hosted Ubuntu 10.04 systems (15th August 2011). The fixed delay time is too regular and still caused the same race condition. A successful resolution was to modify only the relevant action config (in this case iptables-multiport.conf) and insert a random sleep (0.0000 to 2.9999 seconds) before the iptables action, so actionstart becomes:
actionstart = sleep `perl -e 'print rand(3);'`
iptables -N fail2ban-<name>
iptables -A fail2ban-<name> -j RETURN
iptables -I INPUT -p <protocol> -m multiport --dports <port> -j fail2ban-<name>
BUT I have now tried the other method you mentioned. Lets see how it goes.