Currently the main bottleneck in bot's speed is F-Chat's limit on 1 PM message per 2 seconds, and 1 server-type message per 0.5 seconds. And, unfortunately, this is a global limit, meaning that bot has to wait 2 seconds between sending messages to different people.
So, yes, if there are a lot of people playing at the same time, it may become slow. However, for that to really be the case, there should be about 10 people fighting at one time, and sending messages almost at the same time.
A lot of commands are designed in a way to send a message to your partner FIRST, and then send you a promt about it. So, for example, when you use:
!ic Message
In mose cases your partner will receive message almost instantly, and will be able to start typing a reply. And then bot sends you a reply with 2 second delay. So it may seem like it's slow, but it is not really.
Also, we're on RP site, and in a lot of cases we spend more than 10-15 seconds to write a post. More often then not it takes us a few minutes to type a post, and some people may take even more to produce long juicy ones.
So a delay of 2-5 seconds should not be a big problem.
Unfortunately there are no solutions to that. Well, there are: