As it is currently written, the AGGRESSIVE flag is only checked during PULSE_MOBILE (roughly every 10 seconds). This doesn't sound very "aggressive" to me, particularly that a character can move around without triggering "aggressive" behavior by the mob.
Instead of checking every mob in the game every 10 seconds, I am planning on moving the aggressive check to moving characters & mobiles. This shouldn't be approximately resource neutral.
I go a little more in depth at my blog (I make no promises as to the quality of the writing there ;) ).

