Are those adjoining lines in the sdclient_task log? There are no lines between? Normally it shouldn't take that long to send the task status. More information might be needed to know for sure, but it could be that your Core Server is processing things slowly at those times. The task status is processed by the WSVulnerabilityCore web application in the LDAppVulerability application pool in IIS. You might find that it is really busy at that time.
Depending on why it is busy (and slow) there could be a few different solutions. The most common reason for slowness in this area is database access/processing. Check your database for fragmented indexes or other potential performance problems. You can look in the WSVulnerabilityCore.dll.log on your Core server, and there will be some information about any queries that are taking a long time to resolve, as well as some summaries of the work that is being done.
You might also be able to increase the number of worker processes used by LDAppVulnerability. This would give the IIS application pool another process and additional resources if that is the cause of the slow down. You shouldn't increase that drastically, just a bit at a time and it should never exceed the number of CPU cores you have - 1. For example, with a quad-core CPU, it should never be more than 3. (Well, never is not really a good word to use, but... probably shouldn't)