Why use hash tables at all? If you block it only per nick (or $wildsite), it will still allow a group of people to flood you off. There's not really any benefit to allowing you to display the reply to multiple people at once.
So... just use a variable. It's more efficient than creating a hash table just to see if it's being flooded.
if (!%slap.flood) {
set -u2 %slap.flood On
describe ....
}
Though I'd still recommend more than 2 seconds. It doesn't exactly look good to reply every 2 seconds with slaps. 10 seconds would be a good minimum imo.