The more players you have in your log, the longer the addon will take to load therefore slowing your WoW loading.
Because the addon goes to all the players contained in your log before entering the game, it is advised to keep your log player base at a minimum.
If you have more than 150 players in your log, your game loading time will start to increase.

If you are affected by this, your log probably contains a lot of ghost players.
Ghost players are players that do not raid with your guild anymore. Maybe because they left the guild or transferred servers, who knows.

Also, if you have used the "Sync with Armory" feature available in the admin section of the webdkp.com website (which you should never do!), it means that all the players have been added to the log whether they are raiders or not.

What to do then?

You have to delete those ghost players completely! Now, the downside of this, is that you can't go on the website and just delete the players from every table. It simply won't work. They will not appear on your tables anymore but will still remain in every log file you will download.

Here's the ONLY WAY to delete players completely. If you follow exactly the instructions below, you will not get any problems. However I will not be held responsible if you mess up your guild's data:

1/ Download the whole backup of your guild, which will be a CSV file.
Go to the admin tab of the website and look for the "Backups" link.
Once on the Backup page, click the "Download Backup" button.

2/ Download and install (for Windows users) a program called Notepad++. It is a very popular, free and powerful text editor. It will save you a ton of time if you're using it. In fact, this tutorial is meant to be used with that program so... go get it!

3/ Make a duplicate of your backup csv file and place it somewhere safe, in a different place than the file you are going to edit!
If you screw up somewhere, you can always revert back.

4/ Open your csv file with Notepad++.

5/ Press Ctrl+F to open the "Find" popup.
Under the "Replace" tab of that popup, enter "|Player" (without the quotes, and replace Player with the name of the player you wish to remove) in the "Find what" box and leave the "Replace with" box empty. Make sure the search mode is set to "Normal". Then click the "Replace All" button.

6/ Redo the exact same thing but with "Player|" (without the quotes) this time.

7/ Redo the same thing but with ".*Player.*" (without the quotes). Make sure to check the "Regular expression" box as the search mode or it will not work. Then click the "Replace All" button.

Note that if someone is called "Playername" for example, his data will be gone too because Playername contains the word "Player" in it. So be aware!

8/ Repeat from step 5 for every player you wish to remove.

9/ Once you're done, select all the lines in your file by pressing Ctrl+A. All the lines will get highlighted. Then go to TextFX->Text Edit->Delete Blank Lines. This will remove all the blank lines that has been made by the Find&Replace feature.

10/ Finished deleting all the players you wanted to?
If yes, then save your file, head to the website and go back on the Backup page.
Under the "Restore Backup" section, select "Full Restore" from the drop menu where it says "Merge".
Click the "Browse..." button and choose your csv file you just edited and then click the "Upload" button.

Voila