So after some research I uncovered statistics that obviously show that every expansion is a filler expansion, and here I will show my research to prove this:
What do you think? Vote in poll!Code:Burning Crusade "Filler" Expansion Threads: 551 "non-Filler" Expansion Threads: 0 Wrath of the Lich King "Filler" Expansion Threads: 497 "non-Filler" Expansion Threads: 0 Cataclysm "Filler" Expansion Threads: 665 "non-Filler" Expansion Threads: 1 Mists of Pandaria "Filler" Expansion Threads: 1516 "non-Filler" Expansion Threads: 3 Warlords of Draenor "Filler" Expansion Threads: 1722 "non-Filler" Expansion Threads: 0 Legion "Filler" Expansion Threads: 806 "non-Filler" Expansion Threads: 5 Battle for Azeroth "Filler" Expansion Threads: 2066 "non-Filler" Expansion Threads: 0