you can't. there might be mods for it but i don't know of any.

plus healing generates aggro for every mob you or your party is in combat with.
eg. you heal for 500
mob A generates 500 aggro to you
mob B generates 500 aggro to you

for damage, you only generate aggro if you hit that mob.
eg. hit mob A for 500
mob A generates 500 aggro to you
mob B generates no aggro.

the numbers are just examples to explain it. doesn't really work that way as come skills generate more aggro than normal. this would be stated in the description of tht particular skill.

We define aggro to be who the mob is attacking. We define threat to be a numeric value that each mob has towards each player on it's threat list. Note, that even for a normal mob, the target who has aggro is not necessarily the player on it's threat list with the most threat.

that is y klhthreat meter is use for

klh threat meter only works if everybody has the mod iirc.