"DELAYED" inserts in shared hosting environments often cause MySQL to drastically increase CPU usage due to the way it handles these requests. A normal insert takes slightly longer to return, but overall resource usage for the system is drastically less than with the "DELAYED" keyword. The MySQL documentation (found here http://dev.mysql.com/doc/refman/5.5/en/insert-delayed.html) has this to say about using DELAYED inserts:
Note that INSERT DELAYED is slower than a normal INSERT if the table is not otherwise in use. There is also the additional overhead for the server to handle a separate thread for each table for which there are delayed rows. This means that you should use INSERT DELAYED only when you are really sure that you need it.
Please consider changing this behavior in your plugin, as right now my best advice for users causing problems with this is to tell them to discontinue use of your plugin.