I wouldn't take notice of online reports cause they do not show current faction situation accurately. Those are just numbers, and most of those TB members are either players who do not play anymore or mule characters (yeah some people join enemy factions with mule characters for easy points). Sticking your nose out of Tram and visiting Brit gate or Despise from time to time will give you better prospect.
Real situation is:
-Active factions: TB and Minax
-Low activity: Shadowlords
-Inactive: Council of Mages
So if you guys want to bring some life to factions, join CoM.
If you all gonna join Minax, who are you going to kill?