Why restrict it to just level based? There's all sorts of yells we could do based on your state...
Kill ratio:
Positive = current yells
Negative = "Don't hurt me!", "They'll swallow our souls!", "Aieeeeee!", "Run awaaaaay!"
Cavalry:
"Hey ya'll watch this!"
"Team hits build character!"
"Stop looking at me!"
"Nerf ranged!"
Archery:
"Always take the shot!"
"Stop running in front of me!"
"Hold still!"
"Nerf cavalry!"
There could be a whole sophisticated auto-yell system!
