As a player going up against a Heavy, I find myself getting shredded to bits within seconds.
As a Heavy going up against another player, I more often find myself completely unable to take down anything with my mini-gun or lock down any areas consistently.
I realize that aiming for the body helps, as per this question, but is there a better way to track an enemy's movement than "just aim right"? Is my somewhat-outdated computer (slight lag issues) causing me to be a less effective Heavy? Or am I just engaging at the wrong range due to damage falloff?
The original question was about how to better track my aim against targets, which is a bit too broad and doesn't really have an answer, though some of the answers given offered good advice.
Shifting this question a bit, I think my problem may actually be related to target priority.
In other words, who should I be aiming for as a Heavy?
Otherwise...I think this question might be inappropriate, and possibly should be closed.