I must bring attention to the devs to a very serious problem concerning the Tower of Doom event:
In Guild war when a player join a new guild after Monday, he cant play anymore the Guild war in his new guild. Which is perfect and normal.
But for the other Guild based event, Tower of Doom, it is actually possible for guilds who have several sister guilds to rotate players from their secondary guild(s) to add more Doom kills to the total of their main guild!
If devs really care about fair competition, I urge them to quickly change how is working Tower of Doom so it wont be anymore possible for a player joining another guild after Monday to also score and give points to his new guild! Like how Guild war is actually working.
edit: as @Fourdottwoone and @Razzagor rightfully pointed, creating an alt account to play the 4 free sigils at very low Tower levels is another problem than the one I explained.
With a system like in GW, these 2 potential problems would be removed.