Buff Banner mechanics
Shoot rockets at people, fill up a rage bar, get mini crits, right?
Lets go a tad deeper. The buff banner fills up when you have dealt 1500 rage points of damage.
Now, regular damage and rage damage are different. Say you do 100 damage with a rocket to a heavy. He still has 200 health left. Your rage meter is now 100/1500. Shoot him again for a 100 damage, and you get 200 rage points, you are now at 300/1500. Confused yet?
Rage points actually stack with damage. The total amount of damage done during an attack plus the damage the class has taken equals the amount of rage a soldier can get off a class. This explains why sometimes one or two stray rockets can instantly fill up a rage meter, you've hit a heavy that has stayed alive a LONG time with a medics help.
I think you only need 850 rage now, but the instant full rage bar seems to be no bug after all.
http://forums.steampowered.com/forums/s ... ?t=1087238