Changing the number of emotes to a lower amount would likely not stop these kinds of spam bots. I would recommend leveraging the blacklist spam filter instead to block keywords these bots post.
at first they always used 4 emotes plus a message from some random user
so with the !filters emotes limit 3 we stop all of them
a few days later the attack changes and they use only 2,3 emotes and a random message of some one on the chat
the only way can be an option to ban especific nick names or 2 emotes